Mobile communication system

ABSTRACT

The present invention has an object to provide a mobile communication system capable of performing communication between a user equipment device connected to a relay device and a core network if the relay device moves. An RN ( 1508 ) sets a TA of an eNB to be connected with the own device as a TA of the own device. For example, when the RN ( 1508 ) moves along an arrow ( 1500 ), the TA of the RN ( 1508 ) is changed from a first TA ( 1601 ) to which a fourth eNB ( 1525 ) belongs to a third TA ( 1602 ) to which a tenth eNB ( 1505 ) belongs. Upon change of the TA of the RN ( 1508 ) as described above, a user equipment device (UE;  1509 ) transmits a TA update request signal of the own device to a target second MME ( 1501 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. application Ser. No. 14/237,750, filedFeb. 7, 2014, the entire contents of which is incorporated herein byreference. U.S. application Ser. No. 14/237,750 is a National Stage ofInternational Application No. PCT/JP2012/070365, filed Aug. 9, 2012,which is based upon and claims the benefit of priority under 35 U.S.C. §119 from Japanese Patent Application No. 2011-173756.

TECHNICAL FIELD

The present invention relates to a mobile communication system in whicha base station device performs radio communication with a plurality ofmobile terminal devices.

BACKGROUND ART

Commercial service of a wideband code division multiple access (W-CDMA)system among so-called third-generation communication systems has beenoffered in Japan since 2001. In addition, high speed downlink packetaccess (HSDPA) service for achieving higher-speed data transmissionusing a downlink has been offered by adding a channel for packettransmission (high speed-downlink shared channel (HS-DSCH)) to thedownlink (dedicated data channel, dedicated control channel). Further,in order to increase the speed of data transmission in an uplinkdirection, service of a high speed uplink packet access (HSDPA) systemhas been offered. W-CDMA is a communication system defined by the 3rdgeneration partnership project (3GPP) that is the standard organizationregarding the mobile communication system, where the specifications ofRelease 10 version are produced.

Further, new communication systems referred to as long term evolution(LTE) regarding radio areas and system architecture evolution (SAE)regarding the overall system configuration including a core network(merely referred to as network as well) as communication systemsindependent of W-CDMA is studied in 3GPP. This communication system isalso referred to as 3.9 generation (3.9 G) system.

In the LTE, an access scheme, a radio channel configuration and aprotocol are totally different from those of the W-CDMA (HSDPA/HSUPA).For example, as to the access scheme, code division multiple access isused in the W-CDMA, whereas in the LTE, orthogonal frequency divisionmultiplexing (OFDM) is used in a downlink direction and single careerfrequency division multiple access (SC-FDMA) is used in an uplinkdirection. In addition, the bandwidth is 5 MHz in the W-CDMA, while inthe LTE, the bandwidth can be selected from 1.4 MHz, 3 MHz, 5 MHz, 10MHz, 15 MHz and 20 MHz per base station. Further, differently from theW-CDMA, circuit switching is not provided but a packet communicationsystem is only provided in the LTE.

In the LTE, its communication system is configured by a new core networkdifferent from a general packet radio service (GPRS) being a corenetwork of the W-CDMA, and thus, the radio access network of the LTE isdefined as a radio access network independent of the W-CDMA network.

Therefore, for differentiation from the W-CDMA communication system, inthe LTE communication system, a base station that communicates with auser equipment (UE) is referred to as an E-UTRAN NodeB (eNB), and aradio network controller that transmits/receives control data and userdata to/from a plurality of base stations are referred to as an evolvedpacket core (EPC) or access gateway (aGW).

Unicast service and evolved multimedia broadcast multicast service(E-MBMS service) are provided in this LTE communication system. TheE-MBMS service is broadcast multimedia service. The E-MBMS service ismerely referred to as MBMS in some cases. In the E-MBMS service, bulkbroadcast contents such as news, weather forecast and mobile broadcastare transmitted to a plurality of user equipments. This is also referredto as point to multipoint service.

Non-Patent Document 1 (Chapter 4) describes the decisions by 3GPPregarding an overall architecture in the LTE system. The overallarchitecture is described with reference to FIG. 1. FIG. 1 is a diagramillustrating the configuration of the LTE communication system. Withreference to FIG. 1, the evolved universal terrestrial radio access(E-UTRAN) is composed of one or a plurality of base stations 102,provided that a control protocol for a user equipment 101 such as aradio resource control (RRC) and user planes such as a packet dataconvergence protocol (PDCP), radio link control (RLC), medium accesscontrol (MAC) and physical layer (PHY) are terminated in the basestation 102.

The base stations 102 perform scheduling and transmission of a pagingsignal (also referred to as paging messages) notified from a mobilitymanagement entity (MME) 103. The base stations 102 are connected to eachother by means of an X2 interface. In addition, the base stations 102are connected to an evolved packet core (EPC) by means of an S1interface. More specifically, the base station 102 is connected to themobility management entity (MME) 103 by means of an S1_MME interface andconnected to a serving gateway (S-GW) 104 by means of an S1_U interface.

The MME 103 distributes the paging signal to a plurality of or a singlebase station 102. In addition, the MME 103 performs mobility control ofan idle state. When the user equipment is in the idle state and anactive state, the MME 103 manages a list of tracking areas.

The S-GW 104 transmits/receives user data to/from one or a plurality ofbase stations 102. The S-GW 104 serves as a local mobility anchor pointin handover between base stations. Moreover, a PDN gateway (P-GW) isprovided in the EPC, which performs per-user packet filtering and UE-IDaddress allocation.

The control protocol RRC between the user equipment 101 and the basestation 102 performs broadcast, paging, RRC connection management andthe like. The states of the base station and the user equipment in RRCare classified into RRC_IDLE and RRC_CONNECTED. In RRC_IDLE, public landmobile network (PLMN) selection, system information (S1) broadcast,paging, cell re-selection, mobility and the like are performed. InRRC_CONNECTED, the user equipment has RRC connection, is capable oftransmitting/receiving data to/from a network, and performs, forexample, handover (HO) and measurement of a neighbour cell.

The decisions by 3GPP regarding the frame configuration in the LTEsystem described in Non-Patent Document 1 (Chapter 5) are described withreference to FIG. 2. FIG. 2 is a diagram illustrating the configurationof a radio frame used in the LTE communication system. With reference toFIG. 2, one radio frame is 10 ms. The radio frame is divided into tenequally sized subframes. The subframe is divided into two equally sizedslots. The first and sixth subframes contain a downlink synchronizationsignal (SS) per each radio frame. The synchronization signals areclassified into a primary synchronization signal (P-SS) and a secondarysynchronization signal (S-SS).

Multiplexing of channels for multimedia broadcast multicast servicesingle frequency network (MBSFN) and for non-MBSFN is performed on aper-subframe basis. MBSFN transmission is a simulcast transmissiontechnique realized by simultaneous transmission of the same waveformsfrom a plurality of cells. The MBSFN transmission from a plurality ofcells in the MBSFN area is seen as a single transmission by a userequipment. The MBSFN is a network that supports such MBSFN transmission.Hereinafter, a subframe for MBSFN transmission is referred to as MBSFNsubframe.

Non-Patent Document 2 describes a signaling example when MBSFN subframesare allocated. FIG. 3 is a diagram illustrating the configuration of theMBSFN frame. With reference to FIG. 3, a radio frame including the MBSFNsubframes is allocated per radio frame allocation period. The MBSFNsubframe is a subframe allocated for the MBSFN in a radio frame definedby the allocation period and the allocation offset (radio frameallocation offset), and serves to transmit multimedia data. The radioframe satisfying Equation (1) below is a radio frame including the MBSFNsubframes.SFN mod radioFrameAllocationPeriod=radioFrameAllocationOffset  (1)

The MBSFN subframe is allocated with six bits. The leftmost bit definesthe MBSFN allocation for the second subframe (#1). The second bit, thirdbit, fourth bit, fifth bit, and sixth-bit define the MBSFN allocationfor the third subframe (#2), fourth subframe (#3), seventh subframe(#6), eighth subframe (#7), and ninth subframe (#8), respectively. Thecase where the bit indicates “one” represents that the correspondingsubframe is allocated for the MBSFN.

Non-Patent Document 1 (Chapter 5) describes the decisions by 3GPPregarding the channel configuration in the LTE system. It is assumedthat the same channel configuration is used in a closed subscriber groupcell (CSG cell) as that of a non-CSG cell. Physical channels aredescribed with reference to FIG. 4. FIG. 4 is a diagram illustratingphysical channels used in the LTE communication system.

With reference to FIG. 4, a physical broadcast channel (PBCH) 401 is achannel for downlink transmission from the base station 102 to the userequipment 101. A BCH transport block is mapped to four subframes withina 40 ms interval. There is no explicit signaling indicating 40 mstiming. A physical control format indicator channel (PCFICH) 402 is achannel for downlink transmission from the base station 102 to the userequipment 101. The PCFICH notifies the number of OFDM symbols used forPDCCHs from the base station 102 to the user equipment 101. The PCFICHis transmitted in each subframe.

A physical downlink control channel (PDCCH) 403 is a channel fordownlink transmission from the base station 102 to the user equipment101. The PDCCH notifies the resource allocation information of downlinkshared channel (DL-SCH) that is one of the transport channels shown inFIG. 5 described below), resource allocation information of pagingchannel (PCH) that is one of the transport channels shown in FIG. 5, andhybrid automatic repeat request (HARQ) information related to DL-SCH.The PDCCH carries an uplink scheduling grant. The PDCCH carriesacknowledgement (Ack)/negative acknowledgement (Nack) that is a responsesignal to uplink transmission. The PDCCH is referred to as an L1/L2control signal as well.

A physical downlink shared channel (PDSCH) 404 is a channel for downlinktransmission from the base station 102 to the user equipment 101. ADL-SCH (downlink shared channel) that is a transport channel and a PCHthat is a transport channel are mapped to the PDSCH.

A physical multicast channel (PMCH) 405 is a channel for downlinktransmission from the base station 102 to the user equipment 101. Amulticast channel (MCH) that is a transport channel is mapped to thePMCH.

A physical uplink control channel (PUCCH) 406 is a channel for uplinktransmission from the user equipment 101 to the base station 102. ThePUCCH carries Ack/Nack that is a response signal to downlinktransmission. The PUCCH carries a channel quality indicator (CQI)report. The CQI is quality information indicating the quality ofreceived data or channel quality. In addition, the PUCCH carries ascheduling request (SR).

A physical uplink shared channel (PUSCH) 407 is a channel for uplinktransmission from the user equipment 101 to the base station 102. Anuplink shared channel (UL-SCH) that is one of the transport channelsshown in FIG. 5 is mapped to the PUSCH.

A physical hybrid ARQ indicator channel (PHICH) 408 is a channel fordownlink transmission from the base station 102 to the user equipment101. The PHICH carries Ack/Nack that is a response to uplinktransmission. A physical random access channel (PRACH) 409 is a channelfor uplink transmission from the user equipment 101 to the base station102. The PRACH carries a random access preamble.

A downlink reference signal (RS) is a known symbol in a mobilecommunication system. Five types of downlink reference signals aredefined as follows; cell-specific reference signals (CRSs), MBSFNreference signals, demodulation reference signal (DM-RS) beingUE-specific reference signals, positioning reference signals (PRSs), andchannel-state information reference signals (CSI-RSs). The physicallayer measurement objects of a user equipment include reference signalreceived power (RSRP) measurement.

The transport channels described in Non-Patent Document 1 (Chapter 5)are described with reference to FIG. 5. FIG. 5 is a diagram illustratingtransport channels used in the LTE communication system. FIG. 5(A) showsmapping between a downlink transport channel and a downlink physicalchannel. FIG. 5(B) shows mapping between an uplink transport channel andan uplink physical channel.

Downlink transport channels are described. A broadcast channel (BCH) isbroadcast to the entire coverage of a base station (cell). The BCH ismapped to the physical broadcast channel (PBCH).

Retransmission control according to a hybrid ARQ (HARQ) is applied to adownlink shared channel (DL-SCH). The DL-SCH enables broadcast to theentire coverage of the base station (cell). The DL-SCH supports dynamicor semi-static resource allocation. The semi-static resource allocationis also referred to as persistent scheduling. The DL-SCH supportsdiscontinuous reception (DRX) of a user equipment for enabling the userequipment to save power. The DL-SCH is mapped to the physical downlinkshared channel (PDSCH).

The paging channel (PCH) supports DRX of the user equipment for enablingthe user equipment to save power. The PCH is required to broadcast tothe entire coverage of the base station (cell). The PCH is mapped tophysical resources such as the physical downlink shared channel (PDSCH)that can be used dynamically for traffic.

The multicast channel (MCH) is used for broadcast to the entire coverageof the base station (cell). The MCH supports SFN combining of MBMSservice (MTCH and MCCH) in multi-cell transmission. The MCH supportssemi-static resource allocation. The MCH is mapped to the PMCH.

Retransmission control according to a hybrid ARQ (HARQ) is applied to anuplink shared channel (UL-SCH). The UL-SCH supports dynamic orsemi-static resource allocation. The UL-SCH is mapped to the physicaluplink shared channel (PUSCH).

A random access channel (RACH) shown in FIG. 5(B) is limited to controlinformation. The RACH involves a collision risk. The RACH is mapped tothe physical random access channel (PRACH).

The HARQ is described. The HARQ is the technique for improving thecommunication quality of a channel by combination of automatic repeatrequest (ARQ) and error correction (forward error correction). The HARQhas an advantage that error correction functions effectively byretransmission even for a channel whose communication quality changes.In particular, it is also possible to achieve further qualityimprovement in retransmission through combination of the receptionresults of the first transmission and the reception results of theretransmission.

An example of the retransmission method is described. In a case wherethe receiver fails to successfully decode the received data, in otherwords, in a case where a cyclic redundancy check (CRC) error occurs(CRC=NG), the receiver transmits “Nack” to the transmitter. Thetransmitter that has received “Nack” retransmits the data. In a casewhere the receiver successfully decodes the received data, in otherwords, in a case where a CRC error does not occur (CRC=OK), the receivertransmits “AcK” to the transmitter. The transmitter that has received“Ack” transmits the next data.

Examples of the HARQ system include chase combining. In chase combining,the same data is transmitted in the first transmission andretransmission, which is the system for improving gains by combining thedata of the first transmission and the data of the retransmission inretransmission. This is based on the idea that correct data is partiallyincluded even if the data of the first transmission includes an error,and highly accurate data transmission is enabled by combining thecorrect portions of the first transmission data and the retransmissiondata. Another example of the HARQ system is incremental redundancy (IR).The IR is aimed to increase redundancy, where a parity bit istransmitted in retransmission to increase the redundancy by combiningthe first transmission and retransmission, to thereby improve thequality by an error correction function.

Logical channels described in Non-Patent Document 1 (Chapter 6) aredescribed with reference to FIG. 6. FIG. 6 is a diagram illustratinglogical channels used in an LTE communication system. FIG. 6(A) showsmapping between a downlink logical channel and a downlink transportchannel. FIG. 6(B) shows mapping between an uplink logical channel andan uplink transport channel.

A broadcast control channel (BCCH) is a downlink channel for broadcastsystem control information. The BCCH that is a logical channel is mappedto the broadcast channel (BCH) or downlink shared channel (DL-SCH) thatis a transport channel.

A paging control channel (PCCH) is a downlink channel for transmittingchanges of the paging information and system information. The PCCH isused when the network does not know the cell location of a userequipment. The PCCH that is a logical channel is mapped to the pagingchannel (PCH) that is a transport channel.

A common control channel (CCCH) is a channel for transmission controlinformation between user equipments and a base station. The CCCH is usedin a case where the user equipments have no RRC connection with thenetwork. In a downlink direction, the CCCH is mapped to the downlinkshared channel (DL-SCH) that is a transport channel. In an uplinkdirection, the CCCH is mapped to the uplink shared channel (UL-SCH) thatis a transport channel.

A multicast control channel (MCCH) is a downlink channel forpoint-to-multipoint transmission. The MCCH is used for transmission ofMBMS control information for one or several MTCHs from a network to auser equipment. The MCCH is used only by a user equipment duringreception of the MBMS. The MCCH is mapped to the multicast channel (MCH)that is a transport channel.

A dedicated control channel (DCCH) is a channel for point-to-pointtransmission of the dedicated control information between a userequipment and a network. The DCCH is used when a user equipment is inRRC connection. The DCCH is mapped to the uplink shared channel (UL-SCH)in uplink and mapped to the downlink shared channel (DL-SCH) indownlink.

A dedicated traffic channel (DTCH) is a point-to-point communicationchannel for transmission of the user information to a dedicated userequipment. The DTCH exists in uplink as well as downlink. The DTCH ismapped to the uplink shared channel (UL-SCH) in uplink and mapped to thedownlink shared channel (DL-SCH) in downlink.

A multicast traffic channel (MTCH) is a downlink channel for trafficdata transmission from a network to a user equipment. The MTCH is achannel used only by a user equipment during reception of the MBMS. TheMTCH is mapped to the multicast channel (MCH).

CGI represents a cell global identification. ECGI represents an E-UTRANcell global identification. A closed subscriber group cell (CSG cell) isintroduced in the LTE and in long term evolution advanced (LTE-A) anduniversal mobile telecommunication system (UMTS) described below. TheCSG cell is described below (see Chapter 3.1 of Non-Patent Document 3).

The closed subscriber group (CSG) cell is a cell in which subscriberswho are allowed to use are specified by an operator (hereinafter,referred to as “cell for specific subscribers” in some cases). Thespecified subscribers are allowed to access one or more cells of apublic land mobile network (PLMN). One or more cells in which thespecified subscribers are allowed access are referred to as “CSGcell(s)”. Note that access is restricted in the PLMN.

The CSG cell is part of the PLMN that broadcasts a specific CSG identity(CSG ID; CSG-ID) and broadcasts “TRUE” by CSG indication. The authorizedmembers of the subscriber group who have registered in advance accessthe CSG cells using the CSG-ID that is the access permissioninformation.

The CSG-ID is broadcast by the CSG cell or cells. A plurality of CSG-IDsexist in a mobile communication system. The CSG-IDs are used by userequipments (UEs) for making access from CSG-related members easier.

The locations of user equipments are tracked based on an area composedof one or more cells. The locations are tracked for enabling tracking ofthe locations of user equipments and calling user equipments, that is,allowing user equipments to receive calls even in an idle state. An areafor tracking locations of user equipments is referred to as a trackingarea.

A CSG whitelist is a list that may be stored in a universal subscriberidentity module (USIM) in which all CSG IDs of the CSG cells to whichthe subscribers belong are recorded. The CSG whitelist is merelyreferred to as whitelist or allowed CSG list in some cases. The MMEperforms access control for the UEs accessing through CSG cells (seeChapter 4.3.1.2 of Non-Patent Document 9). Specific examples of theaccess by user equipments include attach, combined attach, detach,service request, and tracking area update procedure (see Chapter 4.3.1.2of Non-Patent Document 9).

Service types of a user equipment in an idle state are described below(see Chapter 4.3 of Non-Patent Document 3). The service types of a userequipment in an idle state are classified into a limited service (alsoreferred to as closed service), a normal service, and an operatorservice. The limited service includes emergency calls, an earthquake andtsunami warning system (ETWS), and a commercial mobile alert system(CMAS) on an acceptable cell described below. The normal service (alsoreferred to as standard service) is the service for public use on asuitable cell described below. The operator service is the service foroperators only on a reserved cell described below.

A “suitable cell” is described below. The “suitable cell” is a cell onwhich a UE may camp to obtain a normal service. Such a cell shallfulfill the following conditions (1) and (2).

(1) The cell is part of the selected PLMN or the registered PLMN, orpart of the PLMN of an “equivalent PLMN list”.

(2) According to the latest information provided by a non-access stratum(NAS), the cell shall further fulfill the following conditions (a) to(d):

(a) the cell is not a barred cell;

(b) the cell is part of a tracking area (TA), not part of the list of“forbidden LAs for roaming”, where the cell needs to fulfill (1) above;

(c) the cell shall fulfill the cell selection criteria; and

(d) for a cell specified as CSG cell by system information (SI), theCSG-ID is part of a “CSG whitelist” of the UE, that is, is contained inthe CSG whitelist of the UE.

An “acceptable cell” is described below. The “acceptable cell” is thecell on which a UE may camp to obtain a limited service. Such a cellshall fulfill all the requirements of (1) and (2) below.

(1) The cell is not a barred cell.

(2) The cell fulfills the cell selection criteria.

“Barred cell” is shown in the system information. “Reserved cell” isshown in the system information.

“Camping on a cell” represents the state where a UE has completed thecell selection or reselection process and the UE has selected a cell formonitoring the system information and paging information. A cell onwhich the UE camps is referred to as “serving cell” in some cases.

Base stations referred to as Home-NodeB (Home-NB; HNB) and Home-eNodeB(Home-eNB; HeNB) are studied in 3GPP. HNB/HeNB is a base station for,for example, household, corporation or commercial access service inUTRAN/E-UTRAN. Non-Patent Document 4 discloses three different modes ofthe access to the HeNB and HNB. Specifically, those are an open accessmode, a closed access mode, and a hybrid access mode.

The respective modes have the following characteristics. In the openaccess mode, the HeNB and HNB are operated as a normal cell for a normaloperator. In the closed access mode, the HeNB and HNB are operated as aCSG cell. The CSG cell is a cell where only CSG members are allowedaccess. In the hybrid access mode, the HeNB and HNB are operated as CSGcells that can also be accessed by non-CSG members at the same time. Inother words, a cell in the hybrid access mode (also referred to ashybrid cell) is the cell that supports both the open access mode and theclosed access mode.

According to 3GPP, there is a range of PCIs in all physical cellidentities (PCIs), which is reserved by the network for use by CSG cells(see Chapter 10.5.1.1 of Non-Patent Document 1). Splitting the range ofPCIs is referred to as PCI-split at times. The PCI split information isbroadcast in the system information from the base station to the userequipments being served thereby. To being served by a base station meansto take that base station as a serving cell. Non-Patent Document 5discloses the basic operation of a user equipment using PCI split. Theuser equipment that does not have the PCI split information needs toperform cell search using all PCIs, for example, using all 504 codes.Meanwhile, the user equipment that has the PCI split information iscapable of performing cell search using the PCI split information.

Further, specifications standard of long term evolution advanced (LTE-A)as Release 10 are pursued in 3GPP (see Non-Patent Document 6 andNon-Patent Document 7).

As to the LTE-A system, it is studied that a relay and a relay node (RN)are supported for achieving a high data rate, high cell-edge throughput,new coverage area, and the like. The relay node being a relay device iswirelessly connected to the radio-access network via a donor cell (DonoreNB; DeNB). The network (NW)-to-relay node link shares the samefrequency band (hereinafter, referred to as “frequency band” in somecases) with the network-to-UE link within the range of the donor cell.In this case, the UE in Release 8 can also be connected to the donorcell. The link between a donor cell and a relay node is referred to as abackhaul link, and the link between the relay node and the UE isreferred to as an access link.

As the method of multiplexing a backhaul link in frequency divisionduplex (FDD), the transmission from DeNB to RN is carried out in adownlink (DL) frequency band, and the transmission from RN to DeNB iscarried out in an uplink (UL) frequency band. As the method of dividingresources in relays, a link from DeNB to RN and a link from RN to UE aretime-division multiplexed in one frequency band, and a link from RN toDeNB and a link from UE to RN are also time-division multiplexed in onefrequency band. This enables to prevent, in a relay, the transmission ofthe relay from interfering with the reception of the own relay.

Not only a normal eNB (macro cell) but also so-called local nodes suchas pico eNB (pico cell), HeNB (HNB, CSG cell), node for hotzone cells,relay node, remote radio head (RRH) and repeater are studied in 3GPP.The network composed of various types of cells as described above isalso referred to as a heterogeneous network (HetNet) in some cases.

As to the LTE, the frequency bands (hereinafter, referred to as“operating bands” in some cases) usable for communication have beenpredetermined. Non-Patent Document 8 describes the frequency bands.

As to the LTE-A system, carrier aggregation (CA) is studied, in whichtwo or more component carriers (CCs) are aggregated to support widertransmission bandwidths up to 100 MHz.

A Release 8- or 9-compliant UE, which supports LTE, is capable oftransmission and reception on only the CC corresponding to one servingcell.

Meanwhile, it is conceivable that a Release 10-compliant UE may have thecapability of transmission and reception, only reception, or onlytransmission on the CCs corresponding to a plurality of serving cells atthe same time.

Each CC employs the configuration of Release 8 or 9, and the CA supportscontiguous CCs, non-contiguous CCs, and CCs in different frequencybandwidths. The UE cannot configure the number of uplink CCs (UL CCs)equal to or more than the number of downlink CCs (DL CCs). The CCsconfigured by the same eNBs do not need to provide the same coverage.The CC is compatible with Release 8 or 9.

In CA, an independent HARQ entity is provided per serving cell in uplinkas well as downlink. A transport block is generated per TTI for eachserving cell. Each transport block and HARQ retransmission are mapped toa single serving cell.

In a case where CA is configured, a UE has single RRC connection with aNW. In RRC connection, one serving cell provides NAS mobilityinformation and security input. This cell is referred to as primary cell(PCell). In downlink, a carrier corresponding to PCell is a downlinkprimary component carrier (DL PCC). In uplink, a carrier correspondingto PCell is an uplink primary component carrier (UL PCC).

A secondary cell (SCell) is configured to form a pair of a PCell and aserving cell, in accordance with the UE capability. In downlink, acarrier corresponding to SCell is a downlink secondary component carrier(DL SCC). In uplink, a carrier corresponding to SCell is an uplinksecondary component carrier (UL SCC).

A pair of one PCell and a serving cell configured by one or more SCellsis configured for one UE.

The above-mentioned LTE Advanced (LTE-A) as a further advancedcommunication system regarding radio areas is studied in 3GPP (seeNon-Patent Document 6 and Non-Patent Document 7). The LTE-A is based onthe LTE communication system regarding radio areas and is configured byaddition of several new techniques thereto. The new techniques includethe technique of supporting wider bands (wider bandwidth extension) andthe coordinated multiple point transmission and reception (CoMP)technique. The CoMP which is being studied for LTE-A in 3GPP isdescribed in Non-Patent Document 6 and Non-Patent Document 7.

CoMP implies the technique of improving the coverage of high data rates,improving a cell-edge throughput, and increasing a communication systemthroughput by transmission or reception coordinated among multiplegeographically separated points. The types of CoMP are grouped intodownlink CoMP (DL CoMP) and uplink CoMP (UL CoMP).

In DL CoMP, the PDSCH to one user equipment (UE) is transmitted incooperation among multiple points. The PDSCH to one UE may betransmitted from one point among multiple points or may be transmittedfrom points among multiple points. In DL CoMP, a serving cell refers toa single cell that transmits resource allocation over the PDCCH.

Joint processing (JP) and coordinated scheduling (CS)/coordinatedbeamforming (CB) are studied as the DL CoMP method.

For JP, data is available at each point in a CoMP cooperating set. Typesof JP are grouped into joint transmission (JT) and dynamic cellselection (DCS). In JT, the PDSCH is transmitted from multiple points,specifically, part of or entire CoMP cooperating set, at a time. In DCS,the PDSCH is transmitted from one point in the CoMP cooperating set at atime.

In CS/CB, data is only available in transmission from a serving cell butuser scheduling/beamforming decisions are made with coordination amongcells corresponding to the CoMP cooperating set.

Base stations (NB, eNB, HNB, HeNB), remote radio unit (RRU), remoteradio equipment (RRE), remote radio head (RRH), relay node (RN), and thelike are studied as the units and cells that perform transmission atmultiple points. The unit and cell that perform coordinated multiplepoint transmission are referred to as a multi-point unit and amulti-point cell, respectively.

PRIOR ART DOCUMENTS Non-Patent Documents

-   Non-Patent Document 1: 3GPP TS 36.300 V10.2.0-   Non-Patent Document 2: 3GPP TS 36.331 V10.0.0-   Non-Patent Document 3: 3GPP TS 36.304 V10.0.0 Chapter 3.1, Chapter    4.3, Chapter 5.2.4-   Non-Patent Document 4: 3GPP S1-083461-   Non-Patent Document 5: 3GPP R2-082899-   Non-Patent Document 6: 3GPP TR 36.814 V9.0.0-   Non-Patent Document 7: 3GPP TR 36.912 V9.3.0-   Non-Patent Document 8: 3GPP TS 36.101 V10.0.0-   Non-Patent Document 9: 3GPP TR 23.830 V9.0.0

SUMMARY OF INVENTION Problem to be Solved by the Invention

The communication method in a case where an RN moves has not beenspecifically discussed in 3GPP. In a case where the moving RN issupported by the conventional technique, a problem arises incommunication performed between a UE being served by the RN and anetwork. For example, in a case where the RN installed in a movable bodysuch as an express bus moves, a UE being served by the RN, which iscarried by a passenger, actually moves together with the movable bodybut does not operate as in moving alone. This is because the UE beingserved by the moving RN communicates with the RN and thus does notrecognize that it has moved between cells. The UE being served by themoving RN accordingly does not perform the mobility process to beperformed when the UE moves alone between cells.

In a case where the UE being served by the moving RN does not performthe mobility process, the MME connected to a DeNB newly connected afterthe moving of the RN cannot recognize the presence of the UE, and cannotmanage the mobility of the UE. The MME connected to the DeNB that hasbeen connected before the moving of the RN attempts to communicate withthe UE but is not allowed to communicate with the UE because the UE isnot located in a management range.

The communication between the UE and core network is not allowed in acase where the MME cannot recognize the presence of the UE and cannotperform mobility management as described above.

An object of the present invention is to provide a mobile communicationsystem capable of performing communication between a core network and auser equipment device connected to a relay device even if the relaydevice moves.

Means to Solve the Problem

A mobile communication system of the present invention includes aplurality of base station devices to be connected to a core network, auser equipment device configured to perform radio communications withthe base station devices, and a relay device movably configured to relaythe radio communications between the base station devices and the userequipment device, wherein: the core network includes management meansfor managing the base station devices, the user equipment device, andthe relay device per predetermined tracking area; the relay device sets,as a tracking area to which the own relay device belongs, a trackingarea to which the base station device to be connected with the own relaydevice belongs; and upon judging that the tracking area to which therelay device to be connected with the own user equipment device belongshas been changed, the user equipment device transmits, to the managementmeans, a tracking area update request signal for updating the trackingarea to which the own user equipment device belongs.

Another mobile communication system of the present invention includes aplurality of base station devices to be connected to a core network, auser equipment device configured to perform radio communications withthe base station devices, and a relay device movably configured to relaythe radio communications between the base station devices and the userequipment device, wherein: the core network includes management meansfor managing the base station devices, the user equipment device, andthe relay device per predetermined tracking area; upon judging that atracking area to which the base station device to be connected with theown relay device belongs has been changed, the relay device transmits,to the management means, a tracking area update request signal forupdating a tracking area to which the own relay device belongs; and uponreceipt of the tracking area update request signal from the relaydevice, the management means performs a process of updating the trackingarea to which the relay device belongs and performs a process ofupdating the tracking area to which the user equipment device belongs.

Effects of the Invention

According to the mobile communication system of the present invention,the relay device sets, as a tracking area (hereinafter, also referred toas a “tracking area of the relay device”) to which the own relay devicebelongs, a tracking area (hereinafter, also referred to as a “trackingarea of the base station device”) to which a base station device to beconnected with the own relay device belongs. Upon this, the relay devicemoves, and the base station device to be connected with the relay deviceis changed, so that the tracking area of the relay device is changed.

The tracking area of the relay device is changed as described above,whereby the user equipment device transmits a tracking area updaterequest signal to the management means. Upon this, the tracking area(hereinafter, also referred to as a “tracking area of the user equipmentdevice”) to which the user equipment device belongs is updated. As aresult, if the relay device moves, the management means can recognizeand manage the user equipment device connected to the relay device,allowing for communication between the user equipment device and corenetwork.

According to the other mobile communication system of the presentinvention, upon change of the tracking area of the base station deviceto be connected with the relay device, the relay device transmits atracking area update request signal to the management means. Upon this,the management means performs the process of updating the tracking areaof the relay device and also performs the process of updating thetracking area of the user equipment device. Thus, if the relay devicemoves, the management means can recognize and manage the user equipmentdevice connected to the relay device, allowing for communication betweenthe user equipment device and core network.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating the configuration of an LTEcommunication system.

FIG. 2 is a diagram illustrating the configuration of a radio frame usedin the LTE communication system.

FIG. 3 is a diagram illustrating the configuration of an MBSFN frame.

FIG. 4 is a diagram illustrating physical channels used in the LTEcommunication system.

FIG. 5 is a diagram illustrating transport channels used in the LTEcommunication system.

FIG. 6 is a diagram illustrating logical channels used in the LTEcommunication system.

FIG. 7 is a block diagram showing the overall configuration of an LTEmobile communication system currently under discussion of 3GPP.

FIG. 8 is a block diagram showing the configuration of a user equipment(user equipment 71 of FIG. 7) according to the present invention.

FIG. 9 is a block diagram showing the configuration of a base station(base station 72 of FIG. 7) according to the present invention.

FIG. 10 is a block diagram showing the configuration of an MME (MME unit73 of FIG. 7) according to the present invention.

FIG. 11 is a block diagram showing the configuration of a HeNBGW 74shown in FIG. 7 that is a HeNBGW according to the present invention.

FIG. 12 is a flowchart showing an outline from a cell search to an idlestate operation performed by a user equipment (UE) in the LTEcommunication system.

FIG. 13 is a diagram showing an architecture of a mobile communicationsystem in a case where an RN in Release 10 of 3GPP is provided.

FIG. 14 is a diagram for describing a use case of a mobile RN.

FIG. 15 is a diagram for describing TAs of a UE in a case where an RNmoves.

FIG. 16 is a diagram for describing a TA to which a UE belongs in a casewhere a TAI of the RN is made identical to a TAI of a target DeNB whenthe RN moves.

FIG. 17 is a diagram showing an example of a sequence when an RN movesin a case where a TAI of the RN is made identical to a TAI of a targetDeNB.

FIG. 18 is a diagram for describing a TA to which a UE belongs in a casewhere the TAI of the RN is fixed when the RN moves.

FIG. 19 is a diagram showing an architecture of a mobile communicationsystem including an RN in a case where the information regarding a TA istransmitted and received between an MME for UE and an MME for RN.

FIG. 20 is a diagram for describing an example of a method of managing aTA in an MME for UE.

FIG. 21 is a diagram for describing an example of a method of managing aTA in an MME for RN.

FIG. 22 is a flowchart showing a processing procedure of a HO process ofan RN.

FIG. 23 is a diagram showing a sequence of notifying the informationregarding a TA of a UE when triggered by a TAU process performed duringthe HO process by the RN.

FIG. 24 is a diagram showing a mapping table after a process ofassociating TAI list information of an RN and TAI list information of aUE in the MME for UE.

FIG. 25 is a diagram showing a sequence of notifying the informationregarding a TA of a UE when triggered by an incoming call for a UE.

FIG. 26 is a diagram showing a sequence of a HO process and a TAUprocess in a case where an RN performs inter-MME HO.

FIG. 27 is a diagram showing a sequence in a case where a TAU process ofa UE being served by the RN is activated when triggered by the receiptof a TAU request message from the RN by a target MME.

FIG. 28 is a diagram showing a sequence of activating a data forwardingprocess of the UE.

FIG. 29 is a flowchart showing a processing procedure of a process inwhich an RN judges whether HO is intra-MME HO or inter-MME HO.

FIG. 30 is a diagram showing an architecture of an RN in a case where anMME that manages only a TA to which a mobile RN belongs is provided.

FIG. 31 is a diagram for describing a TA to which a mobile RN belongsand a TA to which a UE being served by the mobile RN belongs.

FIG. 32 is a diagram showing an architecture in a case where an MME formobile RN is configured in a normal MME.

FIG. 33 is a diagram for describing a TA to which a mobile RN belongsand a TA to which a UE being served by the mobile RN belongs in a firstmodification of a fourth embodiment.

FIG. 34 is a diagram for describing a TA to which a mobile RN belongsand a TA to which a UE being served by the mobile RN belongs in a secondmodification of the fourth embodiment.

FIG. 35 is a diagram for describing cases in which a UE in an RRC_Idlestate moves and does not move together with a mobile RN.

FIG. 36 is a diagram showing a sequence when an RN moves in a case wherea TAI of the RN and a TAI of other type of cell are prohibited frombeing included in the same TAI list.

FIG. 37 is a diagram showing a sequence when an RN moves in a case wherean MME manages two TAI lists for one UE.

FIG. 38 is a diagram showing a sequence in which the MME deletes one ofthe TAI lists when the UE changes to an RRC_Connected state.

FIG. 39 is a diagram showing a sequence when an RN moves in a case wherea source MME and a target MME both manage TAI lists for one UE.

FIG. 40 is a diagram showing a sequence in which the MME deletes one ofthe TAI lists when a UE changes to an RRC_Connected state.

FIG. 41 is a diagram showing a sequence in a case where, in a TAUprocess of an RN, the transmission and reception of the informationregarding a UE being served by the RN as well as the transmission andreception of the information regarding the RN are performed between asource MME and a target MME.

FIG. 42 is a diagram showing a sequence in a case where in a TAU processby an RN, a location update process of the RN and a location updateprocess of a UE being served by the RN are both performed.

FIG. 43 is a diagram showing a sequence in which an RN notifies a UEbeing served thereby of a TAU activation request signal in a case wherethe RN has performed the HO process.

FIG. 44 is a diagram showing a sequence in which an MME for RN notifiesa UE being served by an RN of a TAU activation request signal when theRN has performed the HO process.

FIG. 45 is a diagram showing a sequence of a TAU process in a case whereTAU processes of UEs being served by an RN are performed together.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIG. 7 is a block diagram showing an overall configuration of an LTEmobile communication system, which is under discussion of 3GPP. Theoverall system configuration including closed subscriber group (CSG)cells (Home-eNodeBs (Home-eNB; HeNB) of E-UTRAN, Home-NB (HNB) of UTRAN)and non-CSG cells (eNodeB (eNB) of E-UTRAN, NodeB (NB) of UTRAN, and BSSof GERAN) is studied in 3GPP and, as to E-UTRAN, the configuration asshown in FIG. 7 is proposed (see Chapter 4.6.1 of Non-Patent Document1).

FIG. 7 is described. A user equipment device (hereinafter, referred toas “user equipment” or “UE”) 71 is capable of performing radiocommunication with a base station device (hereinafter, referred to as“base station”) 72 and transmits/receives signals through radiocommunication. The base stations 72 are classified into an eNB 72-1 thatis a macro cell and a Home-eNB 72-2 that is a local node. The eNB 72-1has a relatively large-scale coverage as the coverage in a range inwhich communication with the user equipment (UE) 71 is possible. TheHome-eNB 72-2 has a relatively small-scale coverage as the coverage.

The eNB 72-1 is connected to an MME/S-GW unit (hereinafter, referred toas an “MME unit” in some cases) 73 including an MME, S-GW, or MME andS-GW through an S1 interface, and control information is communicatedbetween the eNB 72-1 and the MME unit 73. A plurality of MME units 73may be connected to one eNB 72-1. The MME unit 73 is equivalent tomanagement means. The MME unit 73 is included in the core network. TheeNBs 72-1 are connected to each other by means of an X2 interface, andcontrol information is communicated between the eNBs 72-1.

The Home-eNB 72-2 is connected to the MME unit 73 by means of an S1interface, and the control information is communicated between theHome-eNB 72-2 and the MME unit 73. A plurality of Home-eNBs 72-2 areconnected to one MME unit 73. Or, the Home-eNBs 72-2 are connected tothe MME units 73 through a Home-eNB Gateway (HeNBGW) 74. The Home-eNBs72-2 are connected to the HeNBGW 74 by means of the S1 interface, andthe HeNBGW 74 is connected to the MME units 73 through an S1 interface.One or a plurality of Home-eNBs 72-2 are connected to one HeNBGW 74, andinformation is communicated therebetween through an S1 interface. TheHeNBGW 74 is connected to one or a plurality of MME units 73, andinformation is communicated therebetween through an S1 interface.

The MME unit 73 and HeNBGW 74 are equivalent to host node devices, andcontrol the connection between the user equipment (UE) 71 and each ofthe eNB 72-1 and Home-eNB 72-2 being a base station. The MME unit 73,specifically, an MME and an S-GW forming the MME unit 73, and the HeNBGW74 are equivalent to management means. The MME unit 73 and the HeNBGW 74are included in the core network.

Further, the configuration below is studied in 3GPP. The X2 interfacebetween the Home-eNBs 72-2 is supported. That is, the Home-eNBs 72-2 areconnected to each other by means of the X2 interface, and controlinformation is communicated between the Home-eNBs 72-2. The HeNBGW 74appears to the MME unit 73 as the Home-eNB 72-2. The HeNBGW 74 appearsto the Home-eNB 72-2 as the MME unit 73. The interfaces between theHome-eNBs 72-2 and the MME units 73 are the same, which are the S1interfaces, in both of the case where the Home-eNB 72-2 is connected tothe MME unit 73 through the HeNBGW 74 and the case where the Home-eNB72-2 is directly connected to the MME unit 73. The HeNBGW 74 does notsupport the mobility to the Horne-eNB 72-2 or the mobility from theHome-eNB 72-2 that spans a plurality of MME units 73. The Home-eNB 72-2supports a single cell.

FIG. 8 is a block diagram showing the configuration of the userequipment (user equipment 71 of FIG. 7) according to the presentinvention. The transmission process of the user equipment 71 shown inFIG. 8 is described. First, a transmission data buffer unit 803 storesthe control data from a protocol processing unit 801 and the user datafrom an application unit 802. The data stored in the transmission databuffer unit 803 is transmitted to an encoding unit 804 and is subjectedto an encoding process such as error correction. There may exist thedata output from the transmission data buffer unit 803 directly to amodulating unit 805 without the encoding process. The data encoded bythe encoding unit 804 is modulated by the modulating unit 805. Themodulated data is output to a frequency converting unit 806 after beingconverted into a baseband signal, and then is converted into a radiotransmission frequency. After that, a transmission signal is transmittedfrom an antenna 807 to the base station 72.

The user equipment 71 executes the reception process as follows. Theradio signal is received through the antenna 807 from the base station72. The received signal is converted from a radio reception frequency toa baseband signal by the frequency converting unit 806 and is thendemodulated by a demodulating unit 808. The demodulated data istransmitted to a decoding unit 809 and is subjected to a decodingprocess such as error correction. Among the pieces of decoded data, thecontrol data is transmitted to the protocol processing unit 801, whilethe user data is transmitted to the application unit 802. A series ofprocesses of the user equipment 71 is controlled by a control unit 810.This means that, though not shown in FIG. 8, the control unit 810 isconnected to the respective units 801 to 809.

FIG. 9 is a block diagram showing the configuration of the base station(base station 72 of FIG. 7) according to the present invention. Thetransmission process of the base station 72 shown in FIG. 9 isdescribed. An EPC communication unit 901 performs datatransmission/reception between the base station 72 and the EPCs (such asMME unit 73 and HeNBGW 74). A communication with another base stationunit 902 performs data transmission/reception to/from another basestation. The EPC communication unit 901 and the communication withanother base station unit 902 respectively transmit/receive informationto/from a protocol processing unit 903. The control data from theprotocol processing unit 903, and the user data and control data fromthe EPC communication unit 901 and the communication with another basestation unit 902 are stored in a transmission data buffer unit 904.

The data stored in the transmission data buffer unit 904 is transmittedto an encoding unit 905 and is then subjected to an encoding processsuch as error correction. There may exist the data output from thetransmission data buffer unit 904 directly to a modulating unit 906without the encoding process. The encoded data is modulated by themodulating unit 906. The modulated data is output to a frequencyconverting unit 907 after being converted into a baseband signal, and isthen converted into a radio transmission frequency. After that, atransmission signal is transmitted to one or a plurality of userequipments 71 through an antenna 908.

While, the reception process of the base station 72 is executed asfollows. Radio signals from one or a plurality of user equipments 71 arereceived through the antenna 908. The received signal is converted froma radio reception frequency into a baseband signal by the frequencyconverting unit 907, and is then demodulated by a demodulating unit 909.The demodulated data is transmitted to a decoding unit 910 and is thensubjected to a decoding process such as error correction. Among thepieces of decoded data, the control data is transmitted to the protocolprocessing unit 903, EPC communication unit 901, or communication withanother base station unit 902, while the user data is transmitted to theEPC communication unit 901 and the communication with another basestation unit 902. A series of processes of the base station 72 iscontrolled by a control unit 911. This means that, though not shown inFIG. 9, the control unit 911 is connected to the respective units 901 to910.

The communication with another base station unit 902 is equivalent to anotification unit and an acquisition unit. The transmission data bufferunit 904, encoding unit 905, modulating unit 906, frequency convertingunit 907, antenna 908, demodulating unit 909, and decoding unit 910 areequivalent to a communication unit.

The functions of the Home-eNB 72-2 under discussion of 3GPP aredescribed below (see Chapter 4.6.2 of Non-Patent Document 1). TheHome-eNB 72-2 has the same function as that of the eNB 72-1. Inaddition, the Home-eNB 72-2 has the function of discovering a suitableserving HeNBGW 74 in a case of connection to the HeNBGW 74. The Home-eNB72-2 is connected only to one HeNBGW 74. That is, in a case of theconnection to the HeNBGW 74, the Home-eNB 72-2 does not use the Flexfunction in the S1 interface. When the Home-eNB 72-2 is connected to oneHeNBGW 74, it is not simultaneously connected to another HeNBGW 74 oranother MME unit 73.

The TAC and PLMN ID of the Home-eNB 72-2 are supported by the HeNBGW 74.When the Horne-eNB 72-2 is connected to the HeNBGW 74, selection of theMME unit 73 at “UE attachment” is performed by the HeNBGW 74 instead ofthe Home-eNB 72-2. The Home-eNB 72-2 may be deployed without networkplanning. In this case, the Home-eNB 72-2 is moved from one geographicalarea to another geographical area. Accordingly, the Home-eNB 72-2 inthis case is required to be connected to a different HeNBGW 74 dependingon its location.

FIG. 10 is a block diagram showing the configuration of the MMEaccording to the present invention. FIG. 10 shows the configuration ofan MME 73 a included in the MME unit 73 shown in FIG. 7 described above.A PDN GW communication unit 1001 performs data transmission/receptionbetween the MME 73 a and a PDN GW. A base station communication unit1002 performs data transmission/reception between the MME 73 a and thebase station 72 by means of the S1 interface. In the case where the datareceived from the PDN GW is user data, the user data is transmitted fromthe PDN GW communication unit 1001 to the base station communicationunit 1002 through a user plane communication unit 1003 and is thentransmitted to one or a plurality of base stations 72. In the case wherethe data received from the base station 72 is user data, the user datais transmitted from the base station communication unit 1002 to the PDNGW communication unit 1001 through the user plane communication unit1003 and is then transmitted to the PDN GW.

In the case where the data received from the PDN GW is control data, thecontrol data is transmitted from the PDN GW communication unit 1001 to acontrol plane control unit 1005. In the case where the data receivedfrom the base station 72 is control data, the control data istransmitted from the base station communication unit 1002 to the controlplane control unit 1005.

A HeNBGW communication unit 1004 is provided in the case where theHeNBGW 74 is provided, which performs data transmission/reception bymeans of the interface (IF) between the MME 73 a and the HeNBGW 74according to an information type. The control data received from theHeNBGW communication unit 1004 is transmitted from the HeNBGWcommunication unit 1004 to the control plane control unit 1005. Theprocessing results of the control plane control unit 1005 aretransmitted to the PDN GW through the PDN GW communication unit 1001.The processing results of the control plane control unit 1005 aretransmitted to one or a plurality of base stations 72 by means of the S1interface through the base station communication unit 1002, and aretransmitted to one or a plurality of HeNBGWs 74 through the HeNBGWcommunication unit 1004.

The control plane control unit 1005 includes an NAS security unit1005-1, an SAE bearer control unit 1005-2, and an idle state mobilitymanaging unit 1005-3, and performs an overall process for the controlplane. The NAS security unit 1005-1 provides, for example, security of anon-access stratum (NAS) message. The SAE bearer control unit 1005-2manages, for example, a system architecture evolution (SAE) bearer. Theidle state mobility managing unit 1005-3 performs, for example, mobilitymanagement of an idle state (LTE-IDLE state, which is merely referred toas idle as well), generation and control of paging signaling in an idlestate, addition, deletion, update, and search of a tracking area (TA) ofone or a plurality of user equipments 71 being served thereby, andtracking area list (TA list) management.

The MME 73 a begins a paging protocol by transmitting a paging messageto the cell belonging to a tracking area (TA) with which the UE isregistered. The idle state mobility managing unit 1005-3 may manage theCSG of the Home-eNBs 72-2 to be connected to the MME 73 a, CSG-IDs, anda whitelist.

In the CSG-ID management, the relationship between a user equipmentcorresponding to the CSG-ID and the CSG cell is managed (added, deleted,updated, or searched). For example, it may be the relationship betweenone or a plurality of user equipments whose user access has beenregistered with a CSG-ID and the CSG cells belonging to this CSG-ID. Inthe whitelist management, the relationship between the user equipmentand the CSG-ID is managed (added, deleted, updated, or searched). Forexample, one or a plurality of CSG-IDs with which user registration hasbeen performed by a user equipment may be stored in the whitelist. Theabove-mentioned management related to the CSG may be performed byanother part of the MME 73 a. A series of processes by the MME 73 a iscontrolled by a control unit 1006. This means that, though not shown inFIG. 10, the control unit 1006 is connected to the respective units 1001to 1005.

The function of the MME 73 a under discussion of 3GPP is described below(see Chapter 4.6.2 of Non-Patent Document 1). The MME 73 a performsaccess control for one or a plurality of user equipments being membersof closed subscriber groups (CSGs). The MME 73 a recognizes theexecution of paging optimization as an option.

FIG. 11 is a block diagram showing the configuration of the HeNBGW 74shown in FIG. 7 that is a HeNBGW according to the present invention. AnEPC communication unit 1101 performs data transmission/reception betweenthe HeNBGW 74 and the MME 73 a by means of the S1 interface. A basestation communication unit 1102 performs data transmission/receptionbetween the HeNBGW 74 and the Home-eNB 72-2 by means of the S1interface. A location processing unit 1103 performs the process oftransmitting, to a plurality of Home-eNBs 72-2, the registrationinformation or the like among the data transmitted from the MME 73 athrough the EPC communication unit 1101. The data processed by thelocation processing unit 1103 is transmitted to the base stationcommunication unit 1102 and is transmitted to one or a plurality ofHome-eNBs 72-2 through the S1 interface.

The data only caused to path through (to be transparent) withoutrequiring the process by the location processing unit 1103 is passedfrom the EPC communication unit 1101 to the base station communicationunit 1102, and is transmitted to one or a plurality of Home-eNBs 72-2through the S1 interface. A series of processes by the HeNBGW 74 iscontrolled by a control unit 1104. This means that, though not shown inFIG. 11, the control unit 1104 is connected to the respective units 1101to 1103.

The function of the HeNBGW 74 under discussion of 3GPP is describedbelow (see Chapter 4.6.2 of Non-Patent Document 1). The HeNBGW 74 relaysan S1 application. The HeNBGW 74 terminates the S1 application that isnot linked to the user equipment 71 though it is a part of theprocedures toward the Home-eNB 72-2 and towards the MME 73 a. When theHeNBGW 74 is deployed, the procedure that is not linked to the userequipment 71 is communicated between the Home-eNB 72-2 and the HeNBGW 74and between the HeNBGW 74 and the MME 73 a. The X2 interface is not setbetween the HeNBGW 74 and another node. The HeNBGW 74 recognizes theexecution of paging optimization as an option.

Next, an example of a typical cell search method in a mobilecommunication system is described. FIG. 12 is a flowchart showing anoutline from a cell search to an idle state operation performed by auser equipment (UE) in the LTE communication system. When starting thecell search, in Step ST1201, the user equipment synchronizes the slottiming and frame timing by a primary synchronization signal (P-SS) and asecondary synchronization signal (S-SS) transmitted from a neighbourbase station.

P-SS and S-SS are collectively referred to as synchronization signals(SSs). Synchronization codes, which correspond to physical cellidentities (PCIs) assigned per cell one by one, are assigned to thesynchronization signals (SSs). The number of PCIs is studied in 504ways. These 504 ways are used for synchronization, and the PCIs of thesynchronized cells are detected (specified).

Next, in Step ST1202, the user equipment detects a cell-specificreference signal (CRS) being a reference signal (RS) transmitted fromthe base station per cell and measures the reference signal receivedpower (RSRP). The code corresponding to the PCI one by one is used forthe reference signal (RS), and separation from another cell is enabledby correlation using the code. The code for RS of the cell is derivedfrom the PCI specified in Step ST1201, which makes it possible to detectthe RS and measure the RS received power.

Next, in Step ST1203, the user equipment selects the cell having thebest RS reception quality, for example, cell having the highest RSreceived power, that is, best cell from one or more cells that have beendetected up to Step ST1202.

In Step ST1204, next, the user equipment receives the PBCH of the bestcell and obtains the BCCH that is the broadcast information. A masterinformation block (MIB) containing the cell configuration information ismapped to the BCCH over the PBCH. Accordingly, the MIB is obtained byobtaining the BCCH through reception of the PBCH. Examples of the MIBinformation include the downlink (DL) system bandwidth (also referred toas transmission bandwidth configuration (dl-bandwidth)), transmissionantenna number, and system frame number (SFN).

In Step ST1205, next, the user equipment receives the DL-SCH of the cellbased on the cell configuration information of the MIB, to therebyobtain a system information block (SIB) 1 of the broadcast informationBCCH. The SIB1 includes the information related to the access to thecell, information related to cell selection, and scheduling informationof other SIB (SIBk; k is an integer equal to or larger than two). Inaddition, the SIB1 includes a tracking area code (TAC).

In Step ST1206, next, the user equipment compares the TAC of the SIB1received in Step ST1205 with a TAC portion of the tracking area identity(TAI) in the tracking area (TA) list that has been already possessed bythe user equipment. The tracking area (TA) list is also referred to as aTAI list. TAI denotes TA identity, and is composed of a mobile countrycode (MCC), a mobile network code (MNC), and a tracking area code (TAC).MCC denotes a country code. MNC denotes a network code. TAC denotes a TAcode number.

In a case where the TAC received in Step ST1205 is identical to the TACincluded in the tracking area (TA) list as a result of the comparison,the user equipment enters an idle state operation in the cell. In a casewhere the TAC received in Step ST1205 is not included in the trackingarea (TA) list as a result of the comparison in Step ST1206, the userequipment requires a core network (EPC) including MME and the like tochange a tracking area (TA) through the cell for performing trackingarea update (TAU). The core network updates the tracking area (TA) listbased on an identification number (such as a UE-ID) of the userequipment transmitted from the user equipment together with a TAUrequest signal. The core network transmits the updated tracking area(TA) list to the user equipment. The user equipment rewrites (updates)the TAC list of the user equipment with the received tracking area (TA)list. After that, the user equipment enters the idle state operation inthe cell.

As to the LTE, LTE-A, and universal mobile telecommunication system(UMTS), the introduction of a closed subscriber group (CSG) cell isstudied. As described above, access is allowed for only one or aplurality of user equipments registered with the CSG cell. A CSG celland one or a plurality of user equipments registered with the CSG cellconstitute one CSG. A specific identification number referred to asCSG-ID is added to the thus constituted CSG. Note that one CSG maycontain a plurality of CSG cells. After being registered with any one ofthe CSG cells, the user equipment can access another CSG cell of the CSGto which the registered CSG cell belongs.

Alternatively, the Home-eNB in the LTE and LTE-A or the Home-NB in theUMTS is used as the CSG cell in some cases. The user equipmentregistered with the CSG cell has a whitelist. Specifically, thewhitelist is stored in the subscriber identity module (SIM)/USIM. TheCSG information of the CSG cell with which the user equipment has beenregistered is stored in the whitelist. Specific examples of the CSGinformation include CSG-ID, tracking area identity (TAI), and TAC. Anyone of the CSG-ID and TAC is adequate as long as they are associatedwith each other.

Alternatively, ECGI is adequate as long as the CSG-ID and TAC areassociated with ECGI.

As can be seen from the above, the user equipment that does not have awhitelist (including a case where the whitelist is empty in the presentinvention) is not allowed to access the CSG cell but is allowed toaccess the non-CSG cell only. Meanwhile, the user equipment which has awhitelist is allowed to access the CSG cell of the CSG-ID with whichregistration has been performed as well as the non-CSG cell.

The HeNB and HNB are required to support various services. For example,an operator causes the predetermined HeNB and HNB to register userequipments therein and permits only the registered user equipments toaccess the cells of the HeNB and HNB, which increases radio resourcesavailable for the user equipments and enables high-speed communication.In such a service, the operator correspondingly sets a higher chargethan a normal service.

In order to achieve the above-mentioned service, the closed subscribergroup (CSG) cell accessible only to the registered (subscribed ormember) user equipments is introduced. It is required to install a largenumber of closed subscriber group (CSG) cells in shopping malls,apartment buildings, schools, companies and the like. For example, thefollowing manner of use is required; the CSG cells are installed foreach store in shopping malls, for each room in apartment buildings, foreach classroom in schools, and for each section in companies such thatonly the users who have registered with the respective CSG cells arepermitted to use those CSG cells. The HeNB/HNB is required not only tocomplement the communication outside the coverage of the macro cell(area complementing HeNB/HNB) but also to support various services asdescribed above (service providing HeNB/HNB). This also leads to a casewhere the HeNB/HNB is installed within the coverage of the macro cell.

As described above, it is studied to support a relay and a relay node(RN) as a new technique of LTE-A. The RN supported in Release 10 of 3GPPis a fixed RN and does not move after starting the operation.

FIG. 13 is a diagram showing an architecture of a mobile communicationsystem in a case where the RN in Release 10 of 3GPP is provided. Thearchitecture of the mobile communication system (hereinafter, alsomerely referred to as “communication system”) shown in FIG. 13 isdescribed in TS23.401 V10.3.0 (hereinafter, referred to as “Reference1”) by 3GPP. The mobile communication system includes an MME for RN1301, an MME for UE 1302, a UE 1303, an RN 1304, a DeNB 1305, a P-GW forUE 1306, and an S-GW for UE 1307.

The MME for RN 1301 is an MME that manages the RN 1304. The MME for UE1302 is an MME that manages the MME for UE 1303. The MME for RN 1301 andMME for UE 1302 may be configured in the same MME 1300. FIG. 13 shows acase in which the MME for RN 1301 and MME for UE 1302 are configured inthe same MME 1300. The MME for RN 1301 and MME for UE 1302 are notrequired to be configured in the same MME 1300. The P-GW for UE 1306 isa P-GW for the UE 1303. The S-GW for UE 1307 is an S-GW for the UE 1303.

The UE 1303 and RN 1304 are connected by a Uu interface 1314. The RN1304 and DeNB 1305 are connected by an interface 1315 formed of an S1interface, an X2 interface, and a Un interface. The DeNB 1305 and MMEfor RN 1301 are connected by an S1 interface 1308 and an S11 interface1309. The MME for UE 1302 and DeNB 1305 are connected by an S1 interface1310. The MME for UE 1302 and S-GW for UE 1307 are connected by an S11interface 1311. The DeNB 1305 and S-GW for UE 1307 are connected by anS1 interface 1316. The P-GW for UE 1306 and S-GW for UE 1307 areconnected by an S5/S8 interface 1313. The P-GW for UE 1306 and anexternal packet network are connected by an SGi interface 1312.

As the concept of the architecture of the mobile communication systeminvolving the RN, the RN is recognized as an eNB by the UE andrecognized as a UE by the DeNB.

The DeNB hosts the following two functions in addition to theconventional functions of the eNB (see Non-Patent Document 1).

(1) S1/X2 proxy functionality for supporting one or a plurality of RNs.

(2) S11 termination and S-GW/P-GW functionality for supporting one or aplurality of RNs.

In a case where the RN operates as a UE, communications are performedamong the RN, DeNB, MME for RN, and S-GW/P-GW functionality of the DeNB.The Un interface is used in the communication between the RN and theDeNB. The S1 interface is used in the communication between the DeNB andthe MME for RN. The S11 interface is used in the communication betweenthe MME for RN and the S-GW/P-GW functionality of the DeNB.

Meanwhile, in a case where the RN operates as the eNB for the UE,communications are performed among the UE, RN, S1/X2 proxy functionalityof the DeNB, MME for UE, and S-GW for UE/P-GW for UE. The Uu interfaceis used in the communication between the UE and RN. The S1 interface isused in the communication between the RN and the MME for UE via the S1proxy functionality of the DeNB. The S11 interface is used in thecommunication between the MME for UE and the S-GW for UE/P-GW for UE. Ina case where an X2 interface is used in place of the S1 interface, theUu interface is used in the communication between the UE and RN. The X2interface is used in the communication between the RN and a neighboureNB via the X2 proxy functionality of the DeNB.

In 3GPP, the mobile relay nodes (mobile RNs) are newly proposed inaddition to the fixed RNs. The mobile RNs are disclosed in R1-082975(hereinafter, referred to as “Reference 2”) by 3GPP and R3-110656(hereinafter, referred to as “Reference 3”) by 3GPP.

The mobiles RN are installed in, for example, moving bodies such asexpress buses and high-speed rails and move together therewith. Themobile RN relays the communication between the base station and the userequipment (UE) of a passenger in the moving body, such as an express busand a high-speed rail.

FIG. 14 is a diagram for describing a use case of the mobile RN. A basestation 1402 is located in a coverage 1401 provided by the base station1402. FIG. 14 shows a case in which one base station 1402 provides onecell. In this case, the cell corresponds to the base station 1402. Notlimited to the above, one base station may provide a plurality of cells.In this case, each of the cells corresponds to the base station 1402.The above holds true for the case in which, for example, the basestation is an eNB. This also holds true for the diagrams below.

The moving body, for example, an express bus 1406 is currently locatedwithin the coverage 1401 provided by the base station 1402 and is movingalong the direction of an arrow 1400. An RN 1407 is installed in theexpress bus 1406. Passengers riding in the express bus 1406 carry UEs1403 to 1405. In other words, the UEs 1403 to 1405 are installed in theexpress bus 1406.

The base station 1402 communicates with the RN 1407 moving together withthe express bus 1406. The UEs 1403 to 1405 in the express bus 1406 donot directly communicate with the base station 1402 but communicate withthe base station 1402 via the RN 1407 installed in the express bus 1406.In other words, the RN 1407 appears as a base station to the UEs 1403 to1405 in the express bus 1406.

The following problems arise in the case where the UEs 1403 to 1405 inthe express bus 1406 directly communicate with the macro cell. Theproblems include an impact of the Doppler shift to the UEs, atransmission loss between the inside and outside of a vehicle, areduction in HO success rate, and increases in investment andoperational costs of an operator.

The mobile RN is considered effective as the means for solving thoseproblems. The UE communicates with the mobile RN, resulting in no impactof Doppler shift to the UE and no transmission loss between the insideand outside of a vehicle. The distance between the UE and mobile RN ismuch smaller than the distance between the UE and macro cell, leading toa reduction in consumption power of the UE as well. Further, the UE isconnected to the mobile RN via an air interface and thus does not needto perform HO, which solves signaling congestion. By virtue of theabove, it is not necessary to install a new macro cell, leading toreductions in investment and operational costs of the operator.

Discussions have not been specifically made in 3GPP as to thecommunication method when an RN moves. In a case where the mobile RN issupported by the conventional technique, a problem arises in thecommunication performed between a UE being served by the RN and anetwork. For example, in a case where the RN installed in a moving bodysuch as an express bus moves, the UE being served by the RN, which iscarried by a passenger of the moving body such as an express bus,actually moves together with the moving body but does not operate as inthe case where the UE moves alone. This is because the UE being servedby the moving RN is communicating with this RN and thus does notrecognize that it has moved between cells. Thus, the UE being served bythe moving RN does not perform the mobility process that is performedwhen the UE moves alone between cells.

The problem in a case where the UE does not perform the mobility processis described below. First, a case in which a UE being served by a macrocell moves is described. In this case, the mobility process of the UE isperformed without any trouble.

As described above, the MME manages the TAI list of UE for mobilitymanagement of the UE. The TAT list is shared between the UE and MME. TheTAIs in the TAI list are the TAIs of the TAs managed by the MME thatmanages this TAI list.

For example, in a case where the UE during communication has movedbetween eNBs that are connected to different MMES, the HO process isactivated in the UE. Through the HO process, in order to update the TAto which the own UE belongs to the TA to which a newly connected eNB(hereinafter, also referred to as “target eNB”) belongs, the UE issues aTAU request to an MME (hereinafter, also referred to as “target MME”) tobe connected with the target eNB.

The MME that has received the TAU request performs the process ofmanaging the UE mobility and then transmits the TAT list, by includingthe TAT of the TA to which the target eNB belongs in the TAI list, tothe UE.

This process enables the target MME to recognize the UE and perform themobility management. This allows for communication between the UE andcore network.

The UE activates the TAU process not only during communication but alsoduring moving in an idle state, and thus, a series of processes enablesthe target MME to recognize the UE and perform the mobility management.This allows for communication between the UE and core network.

Next, a case in which the RN moves is described. FIG. 15 is a diagramfor describing the TAs of the UE in a case where the RN moves. First tosixth eNBs (cells) 1522 to 1527 are connected to a first MME 1520 via S1interfaces 1521. Seventh to twelfth eNBs (cells) 1502 to 1507 areconnected to a second MME 1501 via 51 interfaces 1510.

The first to sixth eNBs (cells) 1522 to 1527 are located in first tosixth coverages 1528 to 1533 provided by the eNBs (cells) 1522 to 1577,respectively. Similarly, the seventh to twelfth eNBs (cells) 1502 to1507 are located in seventh to twelfth coverages 1511 to 1516 providedby the eNBs (cells) 1502 to 1507, respectively.

An RN 1508 is located in the coverage 1517 provided by the RN 1508. A UE1509 is served by the RN 1508.

The first, fourth, and fifth eNBs (cells) 1522, 1525, and 1526 belong toa first TA 1534 set in advance. The second, third, and sixth eNBs(cells) 1523, 1524, and 1527 belong to a second TA 1535 set in advance.

The seventh, tenth, and eleventh eNBs (cells) 1502, 1505, and 1506belong to a third TA 1518 set in advance. The eighth, ninth, and twelftheNBs (cells) 1503, 1504, and 1507 belong to a fourth TA 1519 set inadvance.

The first TA 1534 and second TA 1535 are managed by the first MME 1520.The third TA 1518 and fourth TA 1.519 are managed by the second MME1501.

As described above, the MME manages the TAI list of a UE for mobilitymanagement of the UE. The TAI list is shared between the UE and MME. TheTAIs in the TAI list are the TAIs of the TAs managed by the MME thatmanages this TAI list.

For example, in a case where the RN 1508 moves along an arrow 1500 asshown in FIG. 15, it moves between the fourth eNB 1525 and tenth eNB1505, namely between the fourth coverage 1531 and tenth coverage 1514,and the HO process is activated in the RN 1508. The fourth eNB 1525 andtenth eNB 1505 are DeNBs having the functionality for supporting the RN1508.

However, the UE 1509 being served by the RN 1508 that has movedcontinuously communicates with the same RN 1508, and thus does notactivate the HO process. Thus, the UE 1509 being served by the RN 1508that has moved does not activate the TAU.

In the example shown in FIG. 15, the eNB (hereinafter, also referred toas a “source eNB”), to which the RN 1508 has been connected beforemoving, is the fourth eNB 1525, and the MME (hereinafter, also referredto as a “source MME”) connected to the source eNB is the first MME 1520.The target eNB being an eNB, to which the RN 1508 is newly connectedafter moving, is the tenth eNB 1505, and the target MME being an MME tobe connected to the target eNB is the second MME 1501.

The target MME to be connected to the tenth eNB 1505 being the targeteNB of the RN 1508, namely the second MME 1501 cannot receive the TAUrequest from the UE 1509 and accordingly does not recognize the presenceof the UE 1509. Thus, the second MME 1501 cannot perform the mobilitymanagement. The source MME to be connected to the fourth eNB 1525 beingthe source eNB for the RN 1508, namely the first MME 1520 attempts tocommunicate with the UE 1509 but cannot communicate with the UE 1509because the UE 1509 is not located within the management range.

In a case where the MME cannot recognize the presence of the UE and thuscannot perform the mobility management, the UE in the RRC_Connectedstate cannot transmit/receive an NAS message to/from the target MME ifattempting to communicate with the core network side. Also, routing tothe S-GW/P-GW may not be allowed. Thus, communication between the UE andcore network is not allowed.

Also for the UE in the RRC_Idle state, the source MME and target MMEcannot recognize the TA to which the UE belongs. If they cannotrecognize the TA to which the UE belongs, the source MME and target MMEcannot notify the UE of a paging signal. Also, the UE cannot transmit aservice request. Thus, communication is not allowed between the UE andcore network.

This embodiment therefore discloses the method for solving thoseproblems. In this embodiment, the TA to which the RN belongs is madeidentical to the TA to which the target DeNB belongs. In other words,the TAI of the RN is made identical to the TAI of the target DeNB.

FIG. 16 is a diagram for describing the TA to which the UE belongs in acase where the TAI of the RN is made identical to the TAI of the targetDeNB when the RN moves. The configuration shown in FIG. 16 is similar tothe configuration shown in FIG. 15, and thus, the corresponding partsare denoted by the same reference symbols and common description isomitted.

FIG. 16 shows a case in which the RN 1508 moves along the arrow 1500.The TA to which the RN 1508 before moving belongs is the TA to which thefourth eNB 1525 being a source DeNB for the RN belongs. In other words,the TA to which the RN 1508 before moving belongs is a first TA 1601.The first TA 1601 is managed by the first MME 1520. The first, fourth,and fifth eNBs (cells) 1522, 1525, and 1526 belong to the first TA 1601.

After moving, the RN 1508 is connected to the tenth eNB 1505 being aDeNB. The TA to which the RN 1508 after moving belongs is the TA towhich the tenth eNB 1505 being the target DeNB for the RN 1508 belongs.In other words, the TA to which the RN 1508 after moving belongs is athird TA 1602. The third TA 1602 is managed by the second MME 1501. Theseventh, tenth, and eleventh eNBs (cells) 1502, 1505, and 1506 belong tothe third TA 1602.

The RN 1508 moves from the fourth DeNB 1525 to the tenth DeNB 1505,whereby the HO process is activated in the RN 1508. After moving of theRN 1508, the TA to which the RN 1508 belongs changes from the first TA1601 to the third TA 1602. Thus, the RN 1508 activates the TAU processduring the HO process.

The UE 1509 being served by the RN 1508 that has moved continuouslycommunicates with the same RN 1508 and thus does not activate the HOprocess. However, the TA to which the RN 1508 that has moved belongs ischanged from the first TA 1601 to the third TA 1602, and thus, the UE1509 also activates the TAU process.

As described above, the UE 1509 being served by the moving RN 1508activates the TAU process such that the TAU process of the UE isperformed, whereby the target MME 1501, to which the RN 1508 isconnected via the target eNB 1505, can receive the TAU request from theUE 1509. As a result, the TAU process of the UE 1509 enables both of thetarget MME 1501 and source MME 1520 to recognize the presence of the UE1509 and perform mobility management. Thus, communication is allowedbetween the UE and core network.

R3-091335 (hereinafter, referred to as “Reference 4”) by 3GPP describesthat the TAI of the RN is made identical to the TAI of the DeNB, whichis for a fixed RN, but does not disclose the TAI in a case where the RNmoves and further does not disclose a problem arising from the RNmoving.

The method disclosed in this embodiment is aimed to solve theabove-mentioned problem, and as the method therefor, the TAI of the RNis made identical to the TAI of a target DeNB when the RN has moved.Thus, for example, if the TAI of the target DeNB differs from the TAI ofthe source DeNB being a DeNB before moving, the TAI of the RN is alsochanged. In this point, the method disclosed in this embodiment differsgreatly from the technique disclosed in Reference 4.

A specific example for making the TAI of the RN identical to the TAI ofthe target DeNB is disclosed. The RN receives the TAI of the DeNB fromthe DeNB and notifies a UE being served thereby of the TAI. The RN maymake the TAI of the DeNB transparent to the UE. “Making transparent”means the transparent transmission, namely transmission without anychange.

The RN receives the TAI of the DeNB from the DeNB. The RN may receivethe TAC, not TAI. For the TAC, the RN may derive the TAI from the PLMN,MCC, or MNC to be separately received from the DeNB. The TAI can beassociated with the TAC. The following three are disclosed as specificexamples of the method in which the DeNB notifies the RN of the TAI.

(1) The DeNB broadcasts TAI of the TA to which the own DeNB belongs, byincluding it in the system information (SI). The RN receives thebroadcast information broadcast from the DeNB and obtains the TAI.

(2) The DeNB notifies the RN being served thereby of the TAI of the TAto which the own DeNB belongs through dedicated signaling. The RNreceives the dedicated signaling notified from the DeNB and obtains theTAI. The dedicated signaling may be RRC signaling. Alternatively, thesystem information of the DeNB may be notified through dedicatedsignaling. The TAI may be included in the system information.

(3) The source DeNB notifies the RN being served thereby of the TAI ofthe TA to which the target DeNB belongs through dedicated signaling. Thespecific example (3) is applicable to a case in which the TAI of theDeNB is notified in the HO process of the RN. The RN receives thededicated signaling notified from the source DeNB and obtains the TAI ofthe target DeNB. The dedicated signaling may be RRC signaling.Alternatively, the system information of the target DeNB may be notifiedthrough dedicated signaling. The TAI may be included in the systeminformation.

The RN sets the TAI that has been received from the DeNB as the TAI ofthe own RN and broadcasts the TAI as the system information.

FIG. 17 is a diagram showing an example of the sequence when an RN movesin a case where the TAI of the RN is made identical to the TAI of thetarget DeNB.

The RN turns on the power in the coverage of the source DeNB (s-DeNB)and then moves to Step ST1701. In Step ST1701, the RN performs theattach process among the source DeNB, source MME (s-MME), and homesubscriber server (HSS). The HSS corresponds to the management means.The HSS is included in the core network.

During the attach process of Step ST1701, in Step ST1702, the RNreceives RRC signaling including the TAI of the source DeNB from thesource DeNB and obtains the TAI.

In Step ST1703, the RN sets the TAI received from the source DeNB as theTAI of the own RN. Then, in Step ST1704, the RN broadcasts the set TAIas the system information to a UE being served by the own RN.

The UE being served by the RN receives the system information from theRN to recognize the TAT of the RN. The UE checks whether the TAI list ofthe UE includes the TAI of the RN, and performs the TAU process in acase where it is not included or does not perform the TAU process in acase where it is included. FIG. 17 shows the case in which the TAI listof the UE includes the TAI of the RN, namely a case in which the UE doesnot perform the TAU process.

In Step ST1705, the RN moves from the coverage of the source DeNB to thecoverage of the target DeNB.

In Step ST1706, the RN activates the HO such that the HO process of theRN is performed among the source DeNB, target DeNB (t-DeNB), source MME,target MME (t-MME), and HSS.

During the HO process of Step ST1706, in Step ST1707, the RN receivesthe TAI from the target DeNB. Then, the RN checks whether or not the TAIreceived from the target DeNB is included in the TAI list of the own RN,and then performs the TAU process in a case where it is not included ordoes not perform the TAU process in a case where it is included. FIG. 17shows the case in which the TAI list of the RN does not include the TAIreceived from the target DeNB. As described above, in the case where theTAI list of the RN does not include the TAI received from the targetDeNB, the TAU process of the RN is performed among the RN, source DeNB,target DeNB, source MME, target MME, and HSS during the HO process ofStep ST1706.

During the HO process and TAU process of Step ST1706, in Step ST1707,the RN receives RRC signaling including the TAI of the target DeNB fromthe target DeNB and obtains the TAI.

In Step ST1708, the RN changes the TAI of the own RN to the TAI receivedfrom the target DeNB.

In Step ST1709, the RN performs the system information modification (SImodification) process on the UE being served thereby. The RN notifiesthe UE being served thereby of the modification of the systeminformation through paging. Then, in Step ST1710, the RN broadcasts theTAI changed in Step ST1708 to the UE being served thereby as the systeminformation. The UE recognizes that the system information has beenmodified through paging and receives the system information broadcast.This enables the UE being served by the RN to receive the TAI changed ifit is in the RRC_Connected state or RRC_Idle state.

The UE being served by the RN receives the system information from theRN to recognize the TAI of the RN. The UE checks whether or not the TAIof the RN is included in the TAI list of the UE, and then performs theTAU process in a case where it is not included or does not perform theTAU process in a case where it is included. FIG. 17 shows the case inwhich the TAI list of the UE does not include the TAI of the RN, namelya case in which the UE performs the TAU process.

In Step ST1711, the UE activates the TAU process and transmits a TAUrequest signal to the RN.

In Steps ST1712 and ST1714, the RN transmits the TAU request signal fromthe UE to the target MME via the target DeNB.

At this time, in Step ST1713, the target DeNB proxies an 51 message fromthe RN by the S1 proxy functionality for the target MME.

In Step ST1715, the TAU process of the UE is performed among the UE, RN,source DeNB, target DeNB, source MME, target MME, and HSS.

In the TAU process of Step ST1715, the target MME updates the TAI listof the UE and notifies the UE of the updated TAI list. In the TAUprocess, the UE receives the updated TAI list from the target MME.

The method disclosed in this embodiment allows for, in a case where anRN has moved, the activation of the TAU process by the UE being servedthereby that has moved together with the RN. As a result, the target MMEand source MME can manage the TAI list of the UE, such as update anddeletion thereof, allowing the UE and target MME to share the updatedTAI list. This allows for communication between the UE and core network.

In the method disclosed in this embodiment, the RN broadcasts the TAI asthe system information and performs the process of modifying the systeminformation on the UE being served thereby when the TAI is changed. As aresult, the UE being served by the RN activates the TAU process in anyof the RRC_Connected state and RRC_Idle state, and thus can communicatewith the core network.

The method disclosed in this embodiment is applicable not only to thecase in which the RN performs an inter-MME HO but also to the case inwhich the RN performs an intra-MME HO. Also in the intra-MME HO, in acase where the TAI list does not include the TAI of the DeNB, the RNperforms the TAU and changes the TAI of the own RN. Thus, the UE beingserved by the RN activates the TAU and performs the TAU process,allowing the MME to recognize the TA in which the UE is located.

The use of the method of this embodiment allows for the application ofthe same procedure irrespective of HO type, such as inter-MME HO andintra-MME HO. This can simplify the control of allowing thecommunication between the UE being served by the RN and the corenetwork.

The processes of modifying and establishing a bearer for S-GW and P-GWmay be performed in the attach process of the RN, the HO process and TAUprocess of the RN, and the TAU process of the UE, which are not shown inFIG. 17.

In a case where the RN operates as a UE, the S-GW and P-GWfunctionalities for RN are incorporated in the DeNB. In this case,signaling between the MME and S-GW and signaling between the MME andP-GW in the conventional HO sequence may be omitted. It suffices toperform the signaling in the DeNB, which does not require signalingbetween nodes. This results in a reduction in signaling load as asystem.

Second Embodiment

In the method of making the TAI of the RN identical to the TAI of theDeNB, disclosed in the first embodiment, the UEs being served by the RNthat have obtained the changed TAI simultaneously activate the TAU,causing a problem that a large number of TAU requests are issued. Thisresults in a loss of the advantages of the mobile RN described above.

This embodiment discloses the method for solving this problem. In thisembodiment, the TA to which the RN belongs remains unchanged as a resultof moving. In other words, the TAI of the RN is not changed as a resultof moving. The TAI of the RN may be fixed.

FIG. 18 is a diagram for describing the TA to which the UE belongs in acase where the TAI of the RN is fixed when the RN moves. Theconfiguration shown in FIG. 18 is similar to the configuration shown inFIG. 15, and thus, the corresponding parts are denoted by the samereference symbols and common description is omitted.

FIG. 18 shows the case in which the RN 1508 moves along an arrow 1810.The TA to which the RN 1508 before moving belongs is a fifth TA 1801.The fifth TA 1801 is managed by the first MME 1520.

After moving, the RN 1508 is connected to the sixth DeNB 1527. The TA towhich the RN 1508 after moving belongs remains unchanged, which is thefifth TA 1801. The fifth TA 1801 is managed by the first MME 1520.

The RN 1508 moves further and is then connected to the tenth DeNB 1505.The TA to which the RN 1508 after moving belongs remains unchanged,which is the fifth TA 1801. The fifth TA 1801 is managed by the secondMME 1501.

As shown in FIG. 18, in this embodiment, if the RN 1508 moves from thefourth DeNB 1525 to the sixth DeNB 1527 within the same MME, namelywithin the first MME 1520, the TA to which the RN 1508 belongs is stillthe same. In other words, the TAI of the RN 1508 remains unchanged.Here, it is still the fifth TA 1801. If the RN 1508 moves from the sixthDeNB 1527 to the tenth DeNB 1505 between different MMES, namely betweenthe first MME 1520 and second MME 1501, the TA to which the RN 1508belongs is the same. In other words, the TAI of the RN 1508 remainsunchanged. Here, it is still the fifth TA 1801.

Through the above, if an RN moves between DeNBs or between MMEs, the TAIof the RN remains unchanged, and thus, a UE being served by the RN doesnot activate the TAU. As a result, UEs being served by the RN do notactivate the TAU when the RN moves, solving the above-mentioned problem.

The following two are disclosed regarding the TA to which the RNbelongs.

(1) The RN belongs to the TA dedicated thereto.

(2) The RN belongs to a specific TA.

In other words, (1) above means that the TAI of the RN is dedicated tothe RN. In this case, one RN may belong to one TA or a plurality of RNsmay belong to one TA.

As a result of (1) above, a base station (cell) not being an RN does notbelong to the TA to which the RN belongs, making the management in theMME easier. Also, an MME dedicated to an RN can be provided.

The base station (cell) not being an RN does not belong to the TA towhich the RN belongs, allowing for the distinction between aconventional TA configuration dependent on an area and a TAconfiguration dedicated to an RN. Thus, the TA specific to an RN can bemanaged easily even in a case where the RN supports mobility, namely ina case where the RN is movable.

In other words, (2) above means that an RN has a specific TAI. Thespecific TA is a TA to which a specific DeNB (hereinafter, also referredto as “P-DeNB”) connectable with the RN. The P-DeNB may be, for example,the DeNB that is first RRC-connected with the RN. The P-DeNB may be aDeNB that is first RRC-connected after power-off/on of the RN.

The P-DeNB may be a DeNB that is first RRC-connected with the RN amongthe eNBs to be connected to a target MME in cell reselection ininter-MME HO or inter-MME. This does not change the TAI in a case wherethe RN moves within the same MME. As a result, UEs being served by an RNare less likely to simultaneously activate the TAU.

Through (2) above, in a case where, for example, a mobile RN isinstalled in a train, the RN of the train and the DeNBs of whichcoverages cover each station can be configured to belong to the same TA.Also, the DeNBs can be managed by the same MME. As a result, UEs used bytrain passengers can be managed easily.

The RN that supports mobility is a mobile RN, and the RN that does notsupport mobility is a fixed RN. The TA to which the fixed RN belongs andthe TA to which the mobile RN belongs may differ from each other. Forexample, the mobile RN may have a fixed TAI, and the fixed RN may havethe TAI identical to the TAI of the DeNB. This enables only the mobileRN to be managed in a specific TA, allowing for much easier TAmanagement of the RN.

Mobile and fixed modes may be provided as RN modes. One RN may supportboth modes. In a case where one RN can support both modes, the RNoperates in the mobile mode in one case and operates in the fixed modein the other case. The mobile RN may operate in the mobile mode and thefixed RN may operate in the fixed mode. Alternatively, the mobile RN mayoperate in the mobile mode or the fixed mode. The TA to which the RNoperating in the fixed mode belongs and the TA to which the RN operatingin the mobile mode may differ from each other. This allows for TAmanagement according to the operating mode of the RN.

The TAI of the RN and the TAI of the base station (cell) not being an RNmay be distinguished from each other. For example, TAC parts of the TAIsare represented as integers of 0 to 65535. Distinction is made such thatthe TACs for RN are 0 to 32767 and the TACs for other base station are32768 to 65535. The distinction method is not limited to this.

Distinction may be made among the TAIs for mobile RN, TAIs for fixed RN,and TAIs for other eNB. Alternatively, distinction may be made betweenthe TAIs for mobile RN and TAIs for fixed RN and other eNB.

The eNB is fixed and the TA is divided geographically in conventionalcases, and thus, a different TA is managed per MME. The RN, whichsupports mobility, is characterized in “moving”, causing a problem thatwhich MME can manage the TA to which the mobile RN belongs. There is nodiscussion in 3GPP about an MME that manages the TA of the mobile RN.

The following four are disclosed regarding the MME capable of managingthe TA to which the RN supporting mobility belongs.

(1) The TA to which the mobile RN belongs can be managed by anappropriate MME, and the TAI of the mobile RN can be registered in theTAI list served by this MME.

(2) The TA to which the mobile RN belongs can be managed by the MME forthe DeNB, and the TAI of the mobile RN can be registered in the TAI listserved by this MME.

(3) The TA to which the mobile RN belongs can be managed by the MME forthe P-DeNB, and the TAI of the mobile RN can be registered in the TAIlist served by this MME.

(4) The TA to which the mobile RN belongs can be managed by the MME butthe TAI of the mobile RN is not included in the TAI list managed byevery MME.

Through (1) to (4) above, even if the TA to which the RN belongs and theTAI of the RN do not change as a result of moving, the target MME canmanage the TA of this RN.

In a case where the TAI of the RN is not changed as a result of moving,a problem arises in the communication performed between a UE beingserved by the RN and a network. This is because if the RN moves, the UEbeing served by the moving RN is communicating with the RN and does notrecognize that it has moved between cells. Thus, the UE being served bythe moving RN does not perform the mobility process, and the MME cannotconfigure and manage the TAI list of the UE, so that the communicationbetween the UE and core network is not allowed.

The method for solving those problems is therefore disclosed below. TheMME for UE and the MME for RN transmit/receive the information regardingthe TA. An interface (IF) may be newly provided between the MME for UEand the MME for RN for the transmission and reception of theinformation.

FIG. 19 is a diagram showing an architecture of a mobile communicationsystem including an RN in a case where the transmission and reception ofthe information regarding the TA are performed between the MME for UEand the MME for RN. The configuration shown in FIG. 19 is similar to theconfiguration shown in FIG. 13, and thus, the corresponding parts aredenoted by the same reference symbols and common description is omitted.In the configuration shown in FIG. 19, an IF 1901 is provided betweenthe MME for RN 1301 and the MME for UE 1302. The MME for RN 1301 and theMME for UE 1302 transmit and receive the information regarding the TAvia the IF 1901.

The method of managing the TAs in the MME for UE and the MME for RN aredisclosed below. First, the TAs managed by the MME for UE are described.The TAs managed by the MME for UE are for mobility management of a UEbeing served by an RN. Thus, RNs operating as an eNB when viewed from aUE belong to the TA managed by the MME for UE.

FIG. 20 is a diagram for describing an example of the method of managingthe TAs in the MME for UE. The table shown in FIG. 20 is a mapping tableshowing the correspondence between TAs managed by the MME for UE and RNsthat belong thereto. The MME for UE manages the TAs by TAIs and managesthe RNs by identifiers of the RNs. For example, the MME for UE managesthe TAs having TAI#13 and TAI#14. TAI#n (n is an integer not less thanzero) represents the TAI of each TA.

In the example shown in FIG. 20, RNs having RN#0, RN#1, and RN#2 belongto the TA having TAI#13. RNs having RN#3, RN#4, and RN#5 belong to theTA having TAI#14. RN#n (n is an integer not less than zero) representsthe identity of each RN. RN#n may be a cell identity.

For example, if TAI#13 is included in the TAI list (TAI list_UE) of acertain UE, association is made in the MME for UE as follows.

TAI list_UE={TAI#13}={RN#0, RN#1, RN#2}

Next, the TAs managed by the MME for RN are described. The TAs managedby the MME for RN are for mobility management of the RN. Thus, the DeNBsthat operate as an eNB when viewed from the RN belong to the TA managedby the MME for RN.

FIG. 21 is a diagram for describing an example of the method of managingthe TAs in the MME for RN. The table shown in FIG. 21 is a mapping tableshowing the correspondence between the TAs managed by the MME for RN andthe DeNBs that belong thereto. The MME for RN manages the TAs inaccordance with TAIs and manages the DeNBs in accordance with identitiesof DeNBs. For example, the MME for RN manages the TAs having TAI#11 andTAI#12.

DeNBs having DeNB#0 and DeNB#1 belong to the TA having TAI#11. The DeNBshaving DeNB#2 and DeNB#3 belong to the TA having TAI#12. DeNB#n (n is aninteger not less than zero) is an identity of the DeNB. DeNB#n may be acell identity. The MME for RN may manage DeNBs in accordance with eNBidentities as the identities of the DeNBs.

For example, if TAI#11 and TAI#12 are included in the TAI list (TAIlist_RN) of a certain RN, association is made in the MME for RN asfollows.

TAI list_RN#0={TAI#11, TAI#12}={DeNB#0, DeNB#1, DeNB#2, DeNB#3}

Disclosed below is a method of allowing for communication between a UEbeing served by a moving RN and a core network if the UE does notperform a mobility process.

Association is made between the TAI list information (TAI list_UE) ofthe UE managed by the MME for UE and the TAI list information (TAIlist_RN) of the RN managed by the MME for RN. The MME for RN notifiesthe MME for UE of the information regarding the TA of the UE.

This notification may be triggered by the TAU process when the RN movesor may be triggered by an incoming/outgoing call from/to the UE beingserved by the RN that has moved. The method in which anincoming/outgoing call from/to a UE is used as a trigger is suitable forthe case in which a UE being served by an RN is in the RRC_Idle state.

Disclosed below is a specific example of the method of allowing forcommunication between a UE being served by a moving RN and a corenetwork even if the UE does not perform the mobility process.

First, the HO process in a case where the RN has moved is described.FIG. 22 is a flowchart showing a processing procedure of the HO processof the RN.

In Step ST2201, the source DeNB issues, to the source MME, a HO requestof the RN that has moved. Upon generation of the HO request, the processmoves to Step ST2202.

In Step ST2202, the configuration for data forwarding from the sourceDeNB to the target DeNB is performed. After the configuration of dataforwarding, the process moves to Step ST2203.

In Step ST2203, the source DeNB performs data forwarding to the targetDeNB. After data forwarding, the source DeNB moves to Step ST2204. InStep ST2204, a UL opens. After that, the process moves to Step ST2205.

In Step ST2205, the path switch setting from the source DeNB to thetarget DeNB is performed. After the path switch setting, the processmoves to Step ST2206. In Step ST2206, the DL opens. After that, theprocess moves to Step ST2207.

In Step ST2207, the TAU process of the RN is performed as required. TheTAU process is performed in a case where the TAI of the target DeNB isnot included in the TAI list of the RN. This TAU process enables thetarget MME to perform mobility management. After that, the process movesto Step ST2208.

In Step ST2208, the process of releasing an old path before pathswitching is performed. After the process of releasing an old path, theprocess moves to Step ST2209.

In Step ST2209, the HO process is completed. The source MME is identicalto the target MME in a case where the MME is not changed in moving ofthe RN.

Not in the process for a TAU performed in the HO process but in theprocess for TAU alone, the TAU process includes the path switch processof Step ST2205, the TAU process of Step ST2207, and the process ofreleasing an old path of Step ST2208 shown in FIG. 22.

FIG. 23 is a diagram showing a sequence of notifying the informationregarding a TA of a UE, which is triggered by a TAU process performedduring the HO process of the RN. FIG. 23 shows the case of intra-MME HO.

In the TAU process performed during the HO process by the RN, forexample, in the process of Step ST2207 shown in FIG. 22, first, in StepST2301, the RN transmits a TAU request signal to the MME for RN via thetarget DeNB. The TAU process of the RN in Step ST2207 is performed in acase where the TAI list of the RN does not include the TAI of the targetDeNB, as described above. The fact that the TAI list of the RN does notinclude the TAI of the target DeNB means that the TA to which the eNB tobe connected with the RN belongs has been changed. In other words, whenjudging that the TA to which the eNB to be connected with the own RNbelongs has been changed, the RN transmits, to the MME for RN, a TAUrequest signal for updating the TA to which the own RN belongs.

In Step ST2302, the MME for RN performs the TAU process of the RN.Specifically, the MME for RN changes the TAI belongings to the TAI list,as the TAU process of the RN.

In Step ST2303, the MME for RN transmits a TAU acceptance signal to theRN via the target DeNB.

In Step ST2304, the RN transmits a TAU completion signal to the MME forRN via the target DeNB.

In Step ST2301 or ST2304, the RN transmits the identity of the UE beingserved by the RN together with the TAU request signal to be transmittedto the MME for RN. The identity of this UE may be an identity of a UEduring communication. Further, the identity of this RN may betransmitted together.

In Step ST2305, triggered by the receipt of the TAU completion signalfrom the RN, the MME for RN transmits a TAU request signal of the UEbeing served by the RN to the MME for UE.

The MME for RN transmits the TAI list information after the TAU processof the RN, together with the TAU request signal. The identity of the UEbeing served by the RN may be transmitted together. The UE identity maybe an identity of a UE during communication. Further, the identity ofthe RN may be transmitted. These may be transmitted to the MME for UE asanother signal, not being included in the TAU request signal.

In Step ST2306, the MME for UE, which has received the TAU requestsignal of the UE being served by the RN in Step ST2305, associates theTAI list information of the RN with the TAI list information of the UEwith the use of the identity of the UE being served by the RN that hasbeen received together, and the TAI list information of the RN.

For example, the identity of the RN, which has moved from the coverageof the DeNB in the TAI#11 to the coverage of the DeNB in the TAI#12, is#0. Through the TAU process of RN#0, the TAI#12 is newly added to theTAI list. The TAI list after the TAU process is described below.

TAI list_RN#0={TAI#11, TAI#12}={DeNB#0, DeNB#1, DeNB#2, DeNB#3}

Here, the DeNB#0 and DeNB#1 belong to the TAI#11. The DeNB#2 and DeNB#3belong to the TAI#12.

The TAI list (TAI list_UE) of the UE includes the TAI of the RN#0, andthus, the following is shown when this TAI is TAI#13. The RN#0, RN#1,and RN#2 belong to the TAI#13.

TAI list_UE={TAI#13}={RN#0, RN#1, RN#2}

In Step ST2306, the MME for UE associates the TAI list information ofthe RN with the TAI list information of the UE. For example, the RN#0 isreplaced with a DeNB identity in the TAI list_RN#0 as follows.

FIG. 24 is a diagram showing a mapping table after the process ofassociating the TAI list information of the RN with the TAI listinformation of the UE in the MME for UE. The DeNB#0, DeNB#1, DeNB#2,DeNB#3, RN#1, and RN#2 belong to the TAI#13.

Thus, the TAI list of the UE (TAI list_UE) is associated as follows.

TAI list_UE={TAI#13}={RN#0, RN#1, RN#2}={DeNB#0, DeNB#1, DeNB#2, DeNB#3,RN#1, RN#2}

Through the association of the TAI list information of the RN and theTAI list information of the UE as described above, a DeNB that belongsto the TAT of the RN after moving is added to the mapping table of theRNs, eNBs, or DeNBs belonging to the TAI list of the UE. The TAI list ofUE is not changed, but the RN, eNB, or DeNB belonging to the TAI list ofthe UE is changed. In this manner, the MME for UE performs the processof updating a TA to which a UE belongs.

Thus, the MME for UE can recognize to which DeNB the RN to be connectedwith the UE is connected. This enables the MME for UE to performmobility management of the UE being served by an RN, allowing forcommunication between the UE and core network.

Returning to FIG. 23, in Step ST2307, the MME for UE notifies the MMEfor RN of the completion of the process of associating the TAI listinformation of the RN and the TAI list information of the UE.

As described above, as to the MMES including the MME for RN and the MMEfor UE, the MME for RN receives the TAU request signal from the RN,whereby the MME for RN performs the TAU process of the RN and the MMEfor UE performs the TAU process of the UE. This allows for the mobilitymanagement of the RN and the UE being served by the RN even if the RNmoves, allowing for communication between the UE and core network.

While the example above has described the case in which a TAI is added,the same holds true for a case in which a TAI is deleted or changed.

While the example above has disclosed that the RN notifies the MME forUE of the identity of the UE being served thereby in Step ST2305 of FIG.23, not limited thereto. Alternatively, the MME for UE may derive theidentity of the UE being served by this RN from the informationregarding the RN received in Step ST2305.

Next, description is given of the method in which an ongoing call from aUE or an incoming call for a UE is used as a trigger.

FIG. 25 is a diagram showing a sequence of notifying the informationregarding a TA of a UE in the case where an incoming call for a UE isused as a trigger. In the case of the incoming call for the UE, anincoming call signal to be notified the MME for UE is used as a trigger.

When an incoming call is made for the UE, in Step ST2501, the MME for UEreceives an incoming call signal.

Upon receipt of the incoming call signal, in Step ST2502, the MME for UEsearches for the TAI in a TAI list (TAI list_UE) of the UE that hasreceived the incoming call, and obtains an RN identity in the TAI.

Next, in Step ST2503, the MME for UE transmits, to the MME for RN, asignal for requesting the TAI list information of the RN having the RNidentity.

In Step ST2504, the MME for RN searches for the TAI in the TAI list (TAIlist_RN) of the RN having the RN identity, and obtains an eNB identityin the TAI.

In Step ST2505, the MME for RN notifies the MME for UE of the TAI listinformation of the RN. In this case, an eNB identity is included in theTAI list information.

In Step ST2506, the MME for UE associates the TAI list information ofthe RN with the TAI list information of the UE. The process of StepST2506 is identical to the process of Step ST2306 shown in FIG. 23,which is not described here.

Through the processes above, the MME for UE can recognize to which DeNBthe RN to be connected with the UE is connected and thus can perform themobility management of the UE being served by the RN. This allows forcommunication between the UE and core network.

In Steps ST2507 and ST2509, the MME for UE transmits a paging message tothe RN, eNB, and DeNB that belong to the TAI in the TAI list of the UE.

In Step ST2508, the DeNB proxies the paging message for the RN beingserved thereby through the S1 proxy functionality. In Step ST2510, theRN that has received this paging message transmits the paging message tothe UE. This allows for communication between the UE and core network.

In the case of an ongoing call from the UE, in Step ST2501, a servicerequest made by the ongoing call is transmitted from the UE to the MMEfor UE. The processes of Steps ST2502 to ST2506 are performed as in thecase of an incoming call for a UE. Through the processes above, the MMEfor UE can recognize to which DeNB an RN to be connected with a UE isconnected and thus can perform mobility management of the UE beingserved by the RN. This allows for communication between the UE and corenetwork.

The method disclosed in this embodiment can solve a problem that a largenumber of UEs being served by a moving RN simultaneously generate theTAU and also allows for communication between the UEs being served bythe moving RN and the core network even if the UEs do not perform themobility process.

First Modification of Second Embodiment

The second embodiment above has disclosed the method in which with a TAIof an RN being fixed, the information regarding the TA is transmittedand received between the MME for UE and the MME for RN. Thismodification discloses the method of transmitting and receiving theinformation regarding a UE between a target MME and a source MME.

In this modification, in a case where an RN has performed the TAU, theinformation regarding the UE being served by the RN is transmitted andreceived between a source MME and a target MME. The informationregarding the UE being served by the RN may be transmitted and receivedbetween a source MME and a target MME in the HO of the RN. The methoddisclosed in this modification may be applied to a case in which an RNhas performed inter-MME HO.

As described above, an MME that manages a TAI of an RN characterized in“moving” has not been discussed in 3GPP.

This modification discloses an MME in a case where an RN performsinter-MME HO.

The TA for mobile RN belongs to an MME that manages a DeNB. In otherwords, an MME that manages a DeNB manages a TAI for mobile RN.

Through the above, even if a mobile RN moves to a different MME, atarget MME can manage the mobile RN.

While the architecture involving the RN in this case may be identical tothat of FIG. 13, the MME for UE is provided with a function of managinga TA to which a mobile RN belongs. Also, the MME for RN is provided witha function of managing a TAI list of a mobile RN.

Specifically, the TA managed by the MME for UE can be dynamicallyupdated, for example, added or deleted. This allows the MME to add theTAI of the RN that has moved to a DeNB to be connected with the own MMEsuch that the TAI is managed by the own MME. Meanwhile, the MME candelete the TAI of the RN that has moved from the DeNB connected to theown MME from the management by the own MME.

The method disclosed here allows different MMES to manage the same TAI.The TAI of the mobile RN and the TAIs of the eNB and DeNB may beincluded in the same TAI list or may be included in different TAI lists.The UE being served by the mobile RN attaches to the MME to which themobile RN has attached.

In a case where an RN has moved and performed inter-MME HO, the HOprocess and TAU process of the RN are required. The UE being served bythis RN does not need the HO process but needs the TAU process.

In a case where a UE being served by this RN moves between the eNB andRN or between the DeNB and RN, the TAIs of the eNB and DeNB and the TAIof the mobile RN are prohibited from being included in the same TAIlist, so that the UE activates the TAU process. Meanwhile, those TAIsare allowed to be included in the same TAI list, whereby the UE beingserved by the RN does not need to perform the TAU process.

The method disclosed here is also applicable to the first embodimentdescribed above. It suffices that the MME to be connected with thetarget DeNB for the RN manages the TAT of this RN.

In a case where the RN has performed inter-MME HO, the RN activates theHO process shown in FIG. 22, and accordingly, the HO process isperformed among the RN, DeNB, and MME. The TAU process is also performedin a case where the TAI of the DeNB is changed as a result of moving. Inthe case of the inter-MME HO, the MME that manages the TA is changed,whereby the TAI of the DeNB is changed and the TAU process is performed.

However, a UE being served by the RN continuously communicates with theRN and thus does not recognize that it has actually moved. Accordingly,the HO process is not activated in the UE being served by the RN. TheTAU is also not activated, and accordingly, the UE does not transmit theTAU request message to the MME via the RN. As a result, the target MMEdoes not transmit, to the source MME, a message for requesting theinformation regarding the UE, for example, a UE context request message.The target MME cannot recognize the UE being served by the RN that hasmoved and thus cannot manage this UE. Also, the source MME cannotrecognize the UE being served by the RN that has moved and thus cannotmanage this UE.

In order to solve this problem, in a case where an RN has performedinter-MME HO, the information regarding a UE being served by the RN istransmitted and received between the source MME and target MME.

The process of transmitting and receiving the information regarding a UEbeing served by the RN between the source MME and target MME may beperformed during or following the TAU process of the RN. Alternatively,the above-mentioned process may be performed during or following the HOprocess of the RN.

In order to transmit and receive the information regarding a UE beingserved by the RN between the source MME and target MME, the TAU processof this UE may be activated. The information regarding a UE being servedby the RN may be an identity of a UE during communication.

The following three methods are disclosed as specific examples of themethod of activating the TAU process of a UE being served by an RN thathas moved. In the methods below, a predetermined signal is used as atrigger for activating the TAU process of a UE being served by an RNthat has moved. For example, the predetermined signal includes a messagesuch as a TAU request message or a TAU completion message.

(1) The target MME activates the TAU process of a UE being served by anRN, triggered by the receipt of a TAU request message from the RN.

(2) The target MME activates the TAU process of a UE being served by anRN, triggered by the receipt of a TAU completion message from the RN.

(3) The target MME activates the TAU process of a UE being served by anRN, triggered by the detection of a HO completion of the RN.

The specific example (1) above is suitable for a case in which a relatednode has high capacity enough to simultaneously perform the TAU processof an RN and the TAU process of a UE being served by the RN. The TAUprocess of the RN and the TAU process of the UE being served by the RNare performed simultaneously, resulting in a reduction in process delay.

The specific example (2) is suitable for a case in which a related nodecannot simultaneously perform the TAU process of an RN and the TAUprocess of a UE being served by the RN. The specific example (2) is alsoapplicable to a case in which the related node has low processingcapability.

The specific example (3) is also applicable to a case in which a relatednode has low processing capability because the TAU process of a UE beingserved by an RN is performed after the completion of the HO process bythe RN, which further reduces malfunctions.

Disclosed below is a specific example of the method of transmitting andreceiving the information regarding a UE being served by an RN betweenthe source MME and target MME in the HO process and TAU process by theRN.

FIG. 26 is a diagram showing a sequence of the HO process and TAUprocess in a case where an RN performs inter-MME HO. Described below isa case in which the TAU process of a UE being served by a mobile RN isactivated, triggered by the receipt of a TAU request message from the RNby the target MME.

In Step ST2601, communications are performed between a UE being servedby an RN and an RN, source DeNB (s-DeNB), source MME for UE (s-MME forUE) being a source MME for UE, source S-GW for UE (s-S-GW for UE) beinga source S-GW for UE, P-GW for UE, and HSS.

In Step ST2602, the RN moves. As a result, the communication qualitybetween the RN and DeNB deteriorates.

In Step ST2603, the source DeNB receives a measurement result reportmade by the RN to determine a target DeNB, and then transmits a HOrequest signal of the RN to an s-MME for RN being a source MME for RN.

In Step ST2604, the source MME for RN that has received the HO requestsignal in Step ST2603 configures data forwarding among the source DeNB,target DeNB (t-DeNB), source MME for RN, and t-MME for RN being a targetMME for RN.

In Step ST2605, the source MME for RN transmits a HO command signal tothe source DeNB. Then, in Step ST2606, the source DeNB transmits the HOcommand signal to the RN.

In Steps ST2607 and ST2608, the source DeNB transmits DeNB stateinformation to the target DeNB via the source MME for RN and the targetMME for RN.

In Step ST2609, the source DeNB performs data forwarding to the targetDeNB.

In Step ST2610, the RN transmits a HO confirm signal to the target DeNB.In Step ST2611, then, the RN starts the transmission of UL data to thetarget DeNB.

In Step ST2612, the source DeNB transmits a HO notification signal tothe source MME for RN.

In Step ST2613, path switch setting is performed among the source DeNB,target DeNB, source MME for RN, and target MME for RN.

In Step ST2614, the target DeNB starts the transmission of DL data tothe RN.

In Step ST2615, the RN activates a TAU request process, and the TAUprocess is performed among the RN, source DeNB, target DeNB, source MMEfor RN, target MME for RN, and HSS. At this time, the informationregarding a UE being served by an RN is transmitted and received betweenan s-MME for RN being the source MME for RN and a t-MME for RN being thetarget MME for RN.

After the TAU process of Step ST2615, in Step ST2616, the source MME forRN transmits a context release signal to the source DeNB. The sourceDeNB that has received the context release signal releases a contextand, in Step ST2617, transmits a context release completion signal tothe source MME for RN.

In Step ST2618, data forwarding configuration is deleted among thesource MME for RN, source DeNB, target MME for RN, and target DeNB.

In Step ST2619, communications are performed between the UE being servedby the RN and the RN, target DeNB, t-MME for UE being a target MME forUE, t-S-GW for UE being a target S-GW for UE, P-GW for UE, and HSS.

The TAU processing method of a UE being served by an RN is disclosed.FIG. 27 is a diagram showing a sequence in a case where the TAU processof a UE being served by an RN is activated, triggered by the receipt ofa TAU request message from the RN by a target MME. Each process in thesequence shown in FIG. 27 is performed in Step ST2615 of FIG. 26.

In inter-MME HO, the TAI of the target DeNB is not included in the TAIlist of the RN. Thus, in Step ST2701, the RN activates the TAU requestprocess and transmits a TAU request signal to the target MME for RN(t-MME for RA). The RN transmits an identity of a UE being served by theRN together with a TAU request signal to the target MME for RN. Further,an identity of the RN may be transmitted together.

In Step ST2702, the target MME for RN activates a TAU process of a UEbeing served by the RN, triggered by the receipt of the TAU requestsignal from the RN in Step ST2701.

In Step ST2703, the target MME for RN transmits the TAU request signalof the UE being served by the RN to the target MME for UE (t-MME forUE). The target MME for RN transmits an identity of the UE being by theRN together with the TAU request signal to the target MME for UE. Theidentity of the UE being served by the RN may be transmitted to thetarget MME for UE as another signal, not being included in the TAUrequest signal. Alternatively, an identity of the RN may be transmittedtogether. The target MME for UE that has received the TAU request signalof the UE being served by the RN in Step ST2703 activates the TAUprocess of the UE that is represented by the identity of the UE beingserved by the RN, which has been received together.

In Step ST2704, the target MME for RN transmits a context request signalto the source MME for RN (s-MME for RN). In Step ST2705, the target MMEfor UE transmits the context request signal of the UE to the source MMEfor UE (s-MME for UE).

In Step ST2706, the source MME for RN transmits a context responsesignal to the target MME for RN. In Step ST2707, the source MME for UEtransmits a UE context response signal to the target MME for UE.

In Step ST2708, the target MME for RN transmits, to the source MME forRN, a context Ack signal indicating that the context response signaltransmitted from the source MME for RN in Step ST2706 has beensuccessfully accepted. In Step ST2709, the target MME for UE transmits,to the source MME for UE, a UE context Ack signal indicating that the UEcontext response signal transmitted from the source MME for UE in StepST2707 has been successfully accepted.

In Step ST2710, the target MME for RN transmits, to the HSS, a locationupdate request signal for requesting location update of the RN. In StepST2711, the target MME for UE transmits, to the HSS, a UE locationupdate request signal for requesting location update of the UE.

In Step ST2712, the HSS transmits, to the source MME for RN, a locationcancellation request signal for requesting a cancellation of the RNlocation. In Step ST2713, the HSS transmits, to the source MME for UE, aUE location cancellation request signal for requesting a cancellation ofthe UE location.

The source MME for RN that has received the location cancellationrequest signal of the RN in Step ST2712 cancels the location of the RN.In Step ST2714, then, the source MME for RN transmits, to the HSS, alocation cancellation Ack signal indicating that the location of the RNhas been successfully canceled.

The source MME for UE that has received the UE location cancellationrequest signal in Step ST2713 cancels the location of the UE. In StepST2715, then, the source MME for UE transmits, to the HSS, a UE locationcancellation Ack signal indicating that the location of the UE has beensuccessfully canceled.

In Step ST2716, the HSS transmits, to the target MME for RN, a locationupdate Ack signal indicating that the location has been updated. In StepST2717, the HSS transmits, to the target MME for UE, a UE locationupdate Ack signal indicating that the location of the UE has beenupdated.

In Step ST2718, the target MME for RN transmits a TAU acceptance signalto the RN. In Step ST2719, the target MME for UE transmits the TAUacceptance signal of the UE to the UE being served by the RN.

In Step ST2720, the RN transmits a TAU completion signal to the targetMME for RN. Consequently, the TAU processes by the RN have beencompleted in order.

In Step ST2721, the UE being served by the RN transmits the TAUcompletion signal of the UE to the target MME for UE. In Step ST2722,the target MME for UE transmits, to the target MME for RN, the TAUcompletion signal of the UE indicating that the TAU process of the UEbeing served by the RN has been completed. As a result, the TAU processby the UE has been completed in order.

In a case where there is no information to be transmitted to the UE andin a case where there is no change in the information of the TAUacceptance signal, the process of transmitting the TAU acceptance signalto the UE in Step ST2719 and the process of transmitting the TAUcompletion signal from the UE in Step ST2721 may be omitted. In otherwords, in the case where there is no information to be transmitted tothe UE and in the case where there is no change in the information ofthe TAU acceptance signal, the TAU acceptance message to the UE to benotified by the TAU acceptance signal in Step ST2719 and the TAUcompletion message from the UE notified by the TAU completion signal inStep ST2721 may be omitted.

In that case, the target MME for UE receives the location update Acksignal in Step ST2717 and then, in Step ST2722, transmits the TAUcompletion signal of the UE being served by the RN to the target MME forRN.

Through the above, the TAU process of the UE being served by the RN canbe performed in association with the TAU process of the RN that isactivated after moving of the RN. The TAU process of the UE being servedby the RN is performed if the UE being served by the RN does notactivate the TAU process. As a result, the source MME and target MME canrecognize that the UE being served by the RN has moved and can performmobility management. Also, the target MME can configure and manage theTAI list of the UE, allowing for communication between the UE and corenetwork.

In the specific example disclosed in FIG. 27, the TAU process of the RNand the TAU process of the UE are performed simultaneously, triggered bythe receipt of the TAU request signal from the RN by the target MME forRN in Step ST2701. This can reduce a period of time up to the end of theTAU processes by the RN and the UE being served by the RN, resulting ina reduction in process delay as a system.

The TAU request signal to be transmitted from the RN to the target MMEfor RN in Step ST2701 may include the information indicating whether ornot to transmit and receive the information regarding the UE beingserved by the RN between the source MME and target MME. The informationindicating whether or not to perform transmission and reception may be,for example, the information indicating whether or not to perform theTAU process of the UE. A parameter indicative of the above-mentionedinformation may be newly provided to be included in the request signal.This enables the RN to request the MME to perform the TAU process of theUE being served thereby.

As disclosed in this modification, the transmission and reception of theinformation regarding a UE being served by an RN are performed betweenthe source MME and target MME, which enables the source and target MMEsto both perform the mobility management of the UE. As a result, thetarget MME can configure and manage the TAI list of the UE, allowing forcommunication between the UE and core network.

The UE being served by the RN does not need to transmit a TAU requestsignal by the method disclosed in this modification. This can solve aproblem that when the RN moves so as to straddle TAs, UEs being servedby this RN simultaneously generate a TAU request signal. Accordingly,signaling load can be reduced.

For the UEs being served by the RN that has moved, the informationregarding the UEs may be transmitted and received per UE between thesource MME and target MME, or the information regarding the UEsbelonging to a predetermined group or all the UEs may be transmitted andreceived together therebetween.

The information dedicated to a UE and the information common to UEs maybe differentiated so as to be transmitted and received by being includedin a signal as one information element or as one parameter for theinformation common to UEs. This results in a reduction in signalingamong between the MMEs or between the HSS and the MME.

In a case where the TAU process of a UE being served by an RN isperformed during the HO process being performed by the RN, the HOprocess of this RN is desirably performed continuously if the TAUprocess of the UE fails. Alternatively, the HO process may be completed.

In this case, the TAU process of the UE may be performed again. Thenumber of times the TAU process is repeated may be limited.Alternatively, a time limit may be set for allowing the UE to performthe TAU process such that the TAU process can be performed again withinthe time limit. After the time limit has passed, it may be prohibited toperform the TAU process again such that the prohibited UE is notifiedthat the TAU process has failed.

The UE that has been notified that the TAU process has failed maydisconnect the communication with the RN to perform a cell reselectionprocess. Alternatively, the UE activates the TAU process by itself andtransmit a TAU request signal to the target MME via the RN. In otherwords, the UE performs a normal TAU process. This allows the UE toperform the process to be performed in a case where a normal TAU processfails, even if it fails again in connection with the target MME. Thisenables the UE to select other cell such as an eNB, DeNB, or RN,allowing for communication via the selected cell.

Disclosed below is a method in which a target MME notifies a UE via anRN. It suffices that UEs are notified individually, UEs belonging to apredetermined group are notified, or all UEs are notified together.Alternatively, the information regarding UEs belonging to apredetermined group may be notified together or the informationregarding all the UEs may be notified together from the target MME tothe RN, and the information may be notified individually from the RN tothe UE. The information dedicated to a UE and the information common toUEs may be differentiated such that the information common to UEs isnotified as one information element or one parameter.

As the means for notifying a UE by a target MME via an RN, a NAS messageor paging message may be used. In a case where the paging message isused, communication is allowed if the UE in the RRC_Connected state orRRC_Idle state.

An S1 message may be used as the means for notifying an RN by a targetMME, and RRC signaling or MAC signaling may be used as the means fornotifying the UE from the RN. This allows for dedicated notification toa UE in the RRC_Connected state. Notification may be made in the systeminformation as another method of notifying a UE from an RN. This allowsfor notification to a UE in the RRC_Idle state.

A parameter indicative of the information indicating that the TAUprocess of the UE has failed may be provided on the information of atleast one of the NAS message, S1 signaling, RRC signaling, MACsignaling, system information, and paging message to be notified. Thisparameter may be represented as one bit so as to indicate that, forexample, the TAU process has failed in a case of “1”.

In some cases, a UE being served by an RN is restricted from accessingthe target MME. In a case where access is restricted, the UE fails torecognize that it cannot access the target MME, and continues connectionwith the RN. As a result, the UE still cannot communicate with anetwork.

The method of solving this problem is disclosed. In a case where an RNhas moved, the target MME restricts access of a UE being served by theRN. A target MME for UE may be used as the target MME. The target MMEjudges whether or not access it allowed due to access restriction perUE. In a case where access is allowed, the information regarding a UEbeing served by the RN is transmitted and received between the sourceMME and target MME, which has been disclosed in this modification. In acase where access is not allowed, the target MME notifies the UE beingserved by the RN that access is not allowed or access is prohibited.

The method described above may be applied as the operation of the UEnotified that the TAU process has failed. The method described above mayalso be applied as the method of notifying a UE from an RN. Thisenables, also in a case where the UE being served by the RN that hasmoved is restricted from accessing a target MME, the UE to select othercell such as eNB, DeNB, or RN, allowing for communication via theselected cell such as eNB, DeNB, or RN.

It has been disclosed in FIG. 27 that in the case where there is noinformation to be transmitted to a UE being served by an RN from atarget MME or in the case where there is no change in the information tobe transmitted by a TAU acceptance signal, the TAU acceptance message tobe notified the UE from the target MME for UE may be omitted in StepST2719. Specific examples in a case where omission is allowed aredisclosed below.

The above-mentioned specific examples include a case in which a TAI ofan RN remains unchanged as a result of moving and the TAI can be managedby the target MME and a case in which a UE does not need to change aglobally unique temporary identity (GUTI) and an evolved packet system(EPS) bearer.

In the case where there is no change in the TAI in the TAI list of theUE, the TAU acceptance message may be omitted. For example, a TAI of anRN remains unchanged if the RN moves and a TAI list of a UE being servedby the RN includes only the TAI of the RN. This allows for omission ofthe TAI list of the UE.

Even if an RN moves between different MMES, a GUTI to be allocated to aUE being served by an RN by a target MME is made identical to a GUTIallocated to a source MME. This allows for omission of the GUTI. Atarget EPS bearer is made identical to a source EPS bearer, which allowsfor omission of the EPS bearer information.

As a result of the omission of the TAU acceptance message to be notifiedthe UE from the target MME, the UE is not related to the sequence inthis modification. This allows the TAU process of the UE to be performedin the core network, resulting in a reduction in control delay,simplification in control, and reduction in signaling load.

Meanwhile, cases in which a target MME notifies a UE of a TAU acceptancemessage are disclosed, which include (a) a case in which the informationregarding security is notified between a target MME and a UE, (b) a casein which a TAI of an RN cannot be managed also by a target MME, and (c)a case in which a TAI included in a source TAI list cannot be managed bya target MME. In the cases (a) to (c), the target MME may notify the UEof the information (hereinafter, also referred to as “updatedinformation”) updated by the target MME in a TAU acceptance message.

A method similar to the above-mentioned method of notifying theinformation indicating that a TAU process has failed is applicable asthe method of notifying a UE of the updated information from a targetMME.

For only the GUTI provided as the updated information, “GUTIreallocation command” of the NAS message may be notified.

During the HO process being performed by the mobile RN, if the RN is inthe RRC_Connected state with a UE being served thereby, communicationbetween the UE and a core network is not allowed. This case causes aproblem that the UE does not recognize that it is not allowedcommunication and keeps transmitting data to the RN.

The method of solving this problem is disclosed below. An adjustment ismade through scheduling by the RN. It suffices that during the HOprocess being performed by the RN, scheduling is not made in DL as wellas UL. The following three are disclosed as specific examples of thetrigger for interrupting scheduling.

(1) The transmission of a measurement report to a DeNB from an RN isused as a trigger. It suffices that the interruption of scheduling iskept until the measurement report is not transmitted any more.

(2) The reception of a HO command by an RN from a DeNB is used as atrigger. The interruption of scheduling may continue until the RNtransmits a HO confirm to a DeNB.

(3) The radio link failure (RLF) of the RN with the DeNB is used as atrigger. The interruption of scheduling may continue until the mobile RNreturns to the RRC_Connected state.

The data subjected to scheduling and the data subjected to HARQ may becontinuously communicated between the RN and the UE being servedthereby, and the UL data may be held by the RN through buffering. Thedata may be transmitted to the core network side after the completion ofthe HO process by the RN.

In order to prevent the communication with a UE being served by an RN, acommunication hold command may be provided such that the RN notifies theUE being served thereby of the communication hold command. The UE thathas received the communication hold command does not communicate withthe RN.

Through the above, during the HO process being performed by the RN, thebuffer of the RN can be prevented from overflowing or the data can beprevented from being discarded due to the data from the UE being servedby the RN. Also, the UE being served by the RN does not need to receivethe PDCCH per subframe. This allows for a reduction in power consumptionof the UE.

The method disclosed in this modification allows for the TAU process ofthe UE being served by an RN during the HO process being performed bythe RN.

However, the HO process of the UE being served by the RN is notperformed, and accordingly, data forwarding that is performed in thenormal HO process is not performed.

The data forwarding method is disclosed here. In X2 HO, data forwardingis performed between base stations. It suffices that even in a casewhere an RN performs X2 HO, the UE being served by the RN performs dataforwarding within the RN that serves this UE. In other words, dataforwarding outside of the RN becomes unnecessary.

In S1 HO, data forwarding is performed between base stations and betweenS-GWs. In the following description, the data forwarding performedbetween base stations is referred to as “direct forwarding” and the dataforwarding performed between S-GWs is referred to as “indirect dataforwarding”.

The direct forwarding between base stations may be performed by the samemethod as that of the X2 HO described above. The source S-GW or sourceP-GW may activate the HO process of the UE to perform indirectforwarding to the target S-GW or target P-GW. The data forwardingconfiguration of the UE may be activated to perform only the indirectforwarding process. Alternatively, the indirect forwarding may beprohibited to perform only the direct forwarding.

The method of performing a data forwarding process of a UE is disclosed.The data forwarding process of the UE may be performed during the HOprocess of the RN. A specific example of the data forwarding process ofthe UE is described below.

FIG. 28 is a diagram showing a sequence of activating the dataforwarding process of the UE. The data forwarding process of the UEbeing served by the RN may be started, triggered by the receipt of theHO request signal of the RN by the source MME from the source DeNB.

The data forwarding process of the UE is performed between the HOprocess and TAU process of the RN shown in FIG. 26. In Step ST2603 ofFIG. 26, the source DeNB (s-DeNB) transmits the HO request signal of theRN to the source MME for RN (s-MME for RN).

In Step ST2801, the source MME for RN transmits a data forwardingrequest signal of the UE being served thereby to the source MME for UE(s-MME for UE), triggered by the receipt of the HO request signal fromthe source DeNB. A signal for requesting indirect forwarding may betransmitted in place of the data forwarding request signal.

In Step ST2802, the data forwarding configuration of the UE is performedamong the RN, source MME for UE, target MME for UE (t-MME for UE),source S-GW for UE (s-S-GW for UE), and target S-GW for UE (t-S-GW).

In Step ST2803, the source MME for UE transmits, to the RN, a dataforwarding instruction signal for instructing UE data forwarding.

In Step ST2804, the RN performs the UE data forwarding to the targetS-GW for UE via the source S-GW for UE. In Step ST2805, the target S-GWfor UE performs the UE data forwarding to the RN. It suffices thatthrough the data forwardings in Steps ST2804 and ST2805, the data of theUE located in the source S-GW for UE is forwarded to the RN via thetarget S-GW for UE. As a result, the UE data held in the source S-GW forUE is also forwarded to the RN.

In Step ST2806, the data forwarding configuration of the UE is deletedamong the RN, source MME for UE, target MME for UE, source S-GW for UE,and target S-GW for UE. The data forwarding process of the UE may beperformed simultaneously with the HO process and TAU process of the RN.

In activating the HO process of the UE, the source MME for RN transmitsa signal for activating the HO process of the UE being served by the RNto the source MME for RN, triggered by the receipt of the HO requestsignal of the RN from the source DeNB by the source MME for RN. Thesource MME for UE may receive the signal for activating the HO processof the UE being served by the RN to perform the HO process of the UEbeing served by the RN.

The method in which a UE being served by an RN does not need to performthe data forwarding is disclosed. Upon activation of the HO process ofthe RN, the RN interrupts scheduling to the UE being served thereby.This does not require the data transmission and reception between the RNand a UE being served by this RN, whereby data forwarding of the UEbecomes unnecessary. The method described above may be used as themethod in which scheduling to a UE being served by the RN is interruptedduring the HO process being performed by the RN. In a case where thedata forwarding of the UE is necessary, the method described above maybe used for, for example, VoIP.

The method disclosed in this modification allows the target MME andsource MME to recognize a UE being served by the RN and configure andmanage the TAI list of the UE. This allows for communication between theUE and core network.

In a case where the HO process of the UE being served by an RN isperformed during the HO process being performed by the RN, the HOprocess of the RN is preferably continued if the HO process of the UEhas failed. Alternatively, the HO process is preferably completed.

In this case, it suffices that the HO process of the UE is performedagain. The number of times the HO process is repeated may be limited.Or, a time limit may be set for allowing the UE to perform the HOprocess such that the UE can perform the HO process again within thetime limit. After the time limit has passed, the UE may be prohibitedfrom performing the HO process again such that the prohibited UE isnotified that the HO process has failed.

The UE notified that the HO process has failed may disconnect thecommunication with the RN to perform a cell reselection process.Alternatively, the UE may perform a HO failure process. This allows forthe process performed in a case where a normal HO process has failed.This enables the UE to select other cell such as an eNB, DeNB, or RN,allowing for communication via the selected cell.

Third Embodiment

In order to solve a problem that an MME cannot recognize and manage a UEbeing served by an RN that has moved and accordingly the communicationbetween the UE and a network is not allowed, the method disclosed in thefirst embodiment and the method disclosed in the second embodiment maybe combined.

Specifically, in a case where the RN has performed intra-MME HO, themethod disclosed in the second embodiment is applied such that the TAIof the RN is fixed and, only in a case where the RN has performedinter-MME HO, the method disclosed in the first embodiment is appliedsuch that the TAI of the RN is made identical to the TAI of the targetDeNB.

In other words, the method disclosed in the second embodiment is appliedwhen it is judged that the RN has performed intra-MME HO, that is, it isjudged that the TA to which an eNB to be connected with the RN belongshas been changed and when it is judged that no change has been made tothe MME that manages the TA to which an eNB to be connected with the RNbelongs. The method disclosed in the first embodiment is applied when itis judged that an RN has performed inter-MME HO, that is, it is judgedthat the TA to which an eNB to be connected with the RN belongs has beenchanged and when it is judged that a change has been made to the MMEthat manages the TA to which the eNB to be connected with the RNbelongs.

The fixed TAI may be a predetermined TAI managed by the MME to beconnected with the DeNB that serves the RN. The predetermined TAI may bethe TAI to which the P-DeNB belongs.

In a case where the RN has performed inter-MME HO, the RN needs to makethe TAI of the own RN identical to the TAI of the target DeNB. Thefollowing two are disclosed as the method of judging whether the RN hasperformed intra-MME HO or inter-MME HO per se.

(1) The RN judges based on the identity indicating whether or not HO isinter-MME HO notified from the MME.

(2) The RN judges based on the GUTI notified from the target MME when itperforms HO.

In the method (1) above, the MME may be a source MME or target MME. Theidentity indicating whether or not HO is inter-MME HO is provided, andthe MME notifies the RN that performs the HO process of this identity.

A specific example in which a source MME notifies an RN of the identityis disclosed. In a case where the RN has moved and HO has beenactivated, the source MME notifies the RN of a HO command via the sourceDeNB. This HO command may include the identity indicating whether or notHO is inter-MME HO. Alternatively, a signal including the identityindicating whether or not HO is inter-MME HO may be notified separately.

A specific example in which a target MME notifies an RN of the identityis disclosed. In a case where the RN has moved and HO between differentMMEs has been activated, the TAU process of the RN is performed. In theTAU process of the RN, the target MME may notify the RN of the identityindicating whether or not HO is inter-MME HO. For example, the targetMME notifies the RN of a TAU acceptance signal via the target DeNB. TheTAU acceptance signal may include the identity indicating whether or notHO is inter-MME HO. Alternatively, a signal including the identityindicating whether or not HO is inter-MME HO may be notified separately.

The RN judges whether it has performed intra-MME HO or inter-MME HO bythe identity indicating whether or not HO is the inter-MME HO notifiedfrom the MME. The RN can apply the method disclosed in the secondembodiment described above for intra-MME HO and apply the methoddisclosed in the first embodiment described above for inter-MME HO.

A specific example of the method (2) above is disclosed.

When the RN has performed HO, in the HO process or TAU process of theRN, a target MME allocates the GUTI for RN and notifies the RN of theGUTI. The target MME may be a target MME for RN. The RN judges whetherit has performed intra-MME HO or inter-MME HO based on the notifiedGUTI.

As described above, the GUTI is also allocated to the RN similarly tothe user equipment device (UE), allowing the MME to manage the RNidentity by the same identity management method as that in a case wherethe UE identity is managed. This results in simplification of the MMEcontrol.

The GUTI has the number structure described below (see TS23.003 V9.0.0(hereinafter, referred to as “Reference 5”) by 3GPP).

<GUTI>=<GUMMEI><M-TMSI>

The globally unique MME identifier (GUMMEI) is an MME number being anMME identity. The M-temporary mobile subscriber identity (M-TMSI) is anequipment number being a user equipment (UE) identity provided in theMME. The M-TMSI is also allocated to the RN.

FIG. 29 is a flowchart showing a processing procedure of the process inwhich the RN judges whether HO is intra-MME HO or inter-MME HO. The HOprocess or TAU process of the RN is started. For example, in the TAUprocess of Step ST2615 disclosed in FIG. 26, the target MME for RN(t-MME for RN) allocates the GUTI to the RN, and then transmits the TAUacceptance signal, by including the GUTI of the RN in the TAU acceptancesignal, to the RN.

In Step ST2901, the RN receives the GUTI allocated and transmitted tothe own RN by the target MME.

In Step ST2902, the RN derives the GUMMEI from the GUTI transmitted fromthe target MME using the above-mentioned number structure of the GUTI.

In Step ST2903, the RN judges whether or not the GUMMEI derived in StepST2902 is identical to the already obtained GUMMEI of the source MME forRN, which has been transmitted from the source MME for RN. The RN movesto Step ST2904 in a case of judging that the derived GUMMEI is identicalto the GUMMEI of the source MME for RN in Step ST2903 or moves to StepST2905 in a case of judging that the derived GUMMEI is not identical tothe GUMMEI of the source MME for RN in Step ST2903.

In Step ST2904, the RN judges that the target MME is identical to thesource MME and that intra-MME HO has been performed. After the processof Step ST2904, the RN moves to Step ST2906.

In Step ST2906, the RN does not change the TAI of the own RN but followsthe method of the second embodiment described above. In this case, itsuffices that in Step ST2701 shown in FIG. 27 described above, the TAUrequest signal to be transmitted from the RN to the target MME for RNincludes the information indicating whether or not to transmit andreceive the information regarding a UE being served by an RN between thesource MME and target MME. This allows the RN to request the MME toperform the TAU process of the UE being served thereby.

In Step ST2905, the RN judges that the target MME is different from thesource MME and inter-MME HO has been performed. After the process ofStep ST2905, the RN moves to Step ST2907.

In Step ST2907, the RN makes the TAI of the own RN identical to the TAIof the target DeNB. Then, the RN follows the method of the firstembodiment described above. This enables the RN to judge whether HO isintra-MME HO or inter-MME HO. As a result, the RN can apply the methoddisclosed in the second embodiment described above for intra-MME HO orapply the method disclosed in the first embodiment described above forinter-MME HO.

In a case where the RN has performed intra-MME HO, the MME may notnotify the RN of the GUTI. The MME is not changed, and thus, the GUTIdoes not need to be changed.

In this case, in the HO process or TAU process, the RN may judge whetherHO is inter-MME HO or intra-MME HO based on whether or not it has beennewly notified the GUTI from the target MME.

The RN judges that HO is inter-MME HO in a case where it has been newlynotified the GUTI from the target MME or judges that HO is intra-MME HOin a case where it has not been newly notified the GUTI from the targetMME. This results in a reduction in information to be notified the RNfrom the MME.

The method disclosed in the first embodiment described above does notneed a new scheme for the TAU process to be performed by a UE but has aproblem that a large number of TAUs occur simultaneously because UEsbeing served by an RN activate the TAU simultaneously. Meanwhile, themethods disclosed in the second embodiment and the first modification ofthe second embodiment described above can solve the problem that a largenumber of TAUs occur simultaneously but need to exchange the informationregarding a UE between the target MME and source MME especially in thecase of inter-MME HO. This complicates the TAU process of the UE beingserved by the RN.

Application of the method disclosed in this embodiment can reduce thoseproblems. The application of the method disclosed in the secondembodiment described above for intra-MME HO does not need to exchangethe information between different MMEs and does not complicate the TAUprocess. Also, the application of the method disclosed in the firstembodiment only for inter-MME HO can limit the situation where a largenumber of TAUs occur simultaneously to the case of inter-MME HO,reducing a signaling load.

The method disclosed in this embodiment can prevent the control frombecoming complicated, reducing a signaling load. Further, the target MMEand source MME can recognize a UE being served by an RN and configureand manage the TAI list of the UE, allowing for communication betweenthe UE and core network.

Fourth Embodiment

The first to third embodiments above are configured such that the MMEthat manages the TAI of the mobile RN is an MME to be connected with aDeNB. This embodiment discloses another configuration of the MME thatmanages the TAI of the mobile RN.

The MME that manages only the TA to which the mobile RN belongs isprovided. The MME manages the TAI of the mobile RN. The MME manages themobility of the UE being served by the mobile RN.

The following four are disclosed as functions of the MME for mobile RN:

(1) function of managing the TA to which a mobile RN belongs;

(2) function of managing the TAI of a mobile RN;

(3) function of managing the TAs to which a UE being served by a mobileRN belongs and TAIs thereof; and

(4) function of managing the TAI list of a UE being served by a mobileRN.

The MME for mobile RN may have at least one of the above-mentionedfunctions. The MME for mobile RN may have the above-mentioned functionsin addition to the normal functions of the MME.

FIG. 30 is a diagram showing an architecture of a mobile communicationsystem in a case where an MME that manages only a TA to which a mobileRN belongs is provided. The configuration shown in FIG. 30 is similar tothe configuration shown in FIG. 13, and thus, the corresponding partsare denoted by the same reference symbols and common description isomitted.

An m-MME for UE 3003 is an MME that manages only a TA to which an RNbelongs. The DeNB 1305 and m-MME for UE 3003 are connected by an S1interface 3001. The m-MME for UE 3003 and S-GW for UE 1307 are connectedby an S11 interface 3002.

As shown in FIG. 30, the m-MME for UE 3003 that manages the mobility ofthe UE being served by a mobile RN is provided separately from the MMEfor UE 1302 that manages the mobility of the UE being served by a normaleNB or fixed RN.

In a case where the RN 1304 is a fixed RN, the operation is as describedwith reference to FIG. 13. The operation in the case where the RN 1304is a mobile RN is disclosed below.

In a case where the mobile RN 1304 operates as a UE, the operation is asdescribed with reference to FIG. 13. In other words, communications areperformed among the mobile RN 1304, DeNB 1305, MME for RN 1301, andS-GW/P-GW functionality of the DeNB 1305. This is because the MME thatmanages the TAI of the DeNB is an MME for RN, and thus, the MME for RNsuitably manages the mobility of the mobile RN.

Meanwhile, in a case where the mobile RN 1304 operates as an eNB for aUE, communications are performed among the UE 1303, mobile RN 1304,S1/X2 proxy functionality of the DeNB 1305, m-MME for UE 3003, S-GW forUE 1307, and P-GW for UE 1306.

The Uu interface 1314 is used in the communication between the UE 1303and mobile RN 1304. The S1 interface 3001 is used in the communicationbetween the mobile RN 1304 and m-MME for UE 3003 via the S1 proxyfunctionality of the DeNB 1305. The S11 interface 3002 is used in thecommunication between the m-MME for UE 3003 and S-GW for UE 1307.

In a case where an X2 interface is used, the X2 interface is used in thecommunication between the mobile RN 1304 and a neighbour eNB via the X2proxy functionality of the DeNB 1305. This is because the MME thatmanages the TAI of the mobile RN is an m-MME, and thus, the m-MMEsuitably manages the mobility of the UE being served by the mobile RN.The m-MME that manages a UE being served by a mobile RN is referred toas an m-MME for UE.

In the method disclosed in this embodiment, the TAI of the mobile RN andTAIs of other cells such as an eNB, DeNB, and fixed RN are not includedin the same TAI list. Even if the TA to which the DeNB belongs isidentical to the TA to which the mobile RN belongs, they are notincluded in the same TAI list. For example, this is a case in which theTAI of the mobile RN is made identical to the TAI of the target DeNB,which has been disclosed in the first embodiment above.

FIG. 31 is a diagram for describing the TA to which a mobile RN belongsand the TA to which a UE being served by the mobile RN belongs. Theconfiguration shown in FIG. 31 is similar to the configuration shown inFIG. 15, and thus, the corresponding parts are denoted by the samereference symbols and common description is omitted.

FIG. 31 shows a case in which an RN 3106 moves along an arrow 3100. TheRN 3106 is located in a coverage 3107 provided by the RN 3106. The TA towhich the RN 3106 before moving belongs is a fifth TA 3108. A UE 3109being served by the RN 3106 moves as the RN 3106 moves. The RN 3106before moving is connected to the sixth DeNB 1527. The sixth DeNB 1527is connected to the first MME 1520.

After the RN 3106 moves along the arrow 3100, the RN 3106 is connectedto the tenth DeNB 1505. The tenth DeNB 1505 is connected to the secondMME 1501.

The TA to which the RN 3106 after moving belongs remains unchanged,which is the fifth TA 3108. The fifth TA 3108 being a TA to which the RN3106 belongs is managed by an m-MME 3102. The m-MME is connected to allthe DeNBs that support the mobile RN. In the example shown in FIG. 31,the m-MME 3102 is connected to the DeNBs 1522 to 1527 and 1502 to 1507.

As shown in FIG. 31, the mobile RN 3106 moves between different MMEsfrom the sixth DeNB 1527 to the tenth DeNB 1505. In this case, themobile RN still belongs the same TA. In other words, the TAI of the RNremains unchanged. Here, the TAI is still the TAI of the fifth TA 3108.

A DeNB to be connected with the mobile RN is changed, and thus, the HOprocess of the mobile RN is activated. The TA to which a DeNB belongsvaries, that is, the TAI of the DeNB varies, and thus, the mobile RNactivates the TAU in the HO.

Meanwhile, if a mobile RN moves between different DeNBs, the TAI of theRN remains unchanged. Thus, the HO process of the UE being served by themobile RN is not activated, and accordingly, the TAU process thereof isnot activated.

Unlike the first to third embodiments described above, the methoddisclosed in this embodiment causes no problem if the TAU process of theUE is not performed. In this embodiment, an m-MME that manages only theTA to which the mobile RN belongs is provided. This allows the m-MME tomanage the TAI of the mobile RN, to thereby manage the mobility of theUE being served by the mobile RN. In other words, if the mobile RN movesbetween different DeNBs, the m-MME being the MME that manages themobility of the UE being served by the mobile RN remains unchanged.Therefore, if the TAU process of the UE being served by the mobile RN isnot performed, the m-MME can continuously manage the mobility of the UE,without any problem.

The functions of the MME for RN may be divided into the managementfunction for fixed RN and the management function for mobile RN. The MMEfor RN may have the management function for fixed RN, and may beprovided with an m-MME for RN that has the management function formobile RN. The m-MME for UE and m-MME for RN may be configured in thesame MME. This allows the mobility as a mobile RN to be managedseparately from other cells (eNB, DeNB, and fixed RN). The MME for onlya mobile RN can be configured, allowing for flexible additionalinstallation and operation. As a result, investment and operation costscan be reduced.

The method disclosed in this embodiment enables the m-MME to configureand manage the TAI list of the UE if, for example, the TAU process ofthe UE being served by the RN is not performed as disclosed in the firstto the third embodiments. This allows for communication between the UEand core network.

An enormous number of mobile RNs makes it difficult to manage the TAIsof the mobile RNs by one m-MME. The number of DeNBs that support theenormous number of mobile RNs also becomes enormous, which particularlymakes it difficult for one m-MME to be connected to all the DeNBs. Themethod of solving this problem is disclosed below.

The mobile RNs are subjected to grouping. The DeNBs that support themobile RNs are limited for each of the group. An m-MME that manages theTAI of the mobile RN is provided for each of the groups.

The provision of an m-MME for each group of the mobile RNs can limit theDeNBs to be connected with each m-MME. This eliminates the need forconnecting one m-MME with an enormous number of DeNBs.

Grouping of mobile RNs may be performed, for example, per service, suchas a group to be installed in a car of XX bullet train and a group to beinstalled in a car of YY bullet train.

If the DeNB that supports a mobile RN is not connected to the m-MME, themobility of the UE being served by the RN is not managed by the m-MME.The following three are disclosed as the methods of solving thisproblem.

(1) The UE is not allowed to communicate.

(2) The management of the TAI of the mobile RN is moved to the MME onwhich the mobile RN has performed the TAU.

(3) The TAI of the mobile RN is changed to the TAI of the DeNB.

The method (1) above is suitable for a case in which the access of amobile RN is limited to a desired m-MME. For example, in a case whereafter moving, a group of a certain mobile RN is connected to a DeNBconnected to an m-MME that manages a TAI of another mobile RN, the UEbeing served by this mobile RN is not allowed to communicate. Thisallows for communication of only a UE being served by a mobile RN in agroup.

The management of the TAI of the mobile RN is moved to the MME on whichthe mobile RN has performed the TAU, as in the method (2) above,allowing for communication of a UE being served by this RN.

The method (3) above is the method disclosed in the first embodimentdescribed above, achieving effects of the first embodiment above.

In the method disclosed in this embodiment, if a mobile RN performsinter-MME HO, the MME that manages the TAI of the UE being served bythis RN is an m-MME and is not changed. This eliminates the need forperforming the TAU process of the UE. As a result, the problem that alarge number of TAUs occur simultaneously, which is caused in themethods disclosed in the first to third embodiments above, can besolved. Further, it is not required to exchange information between thesource MME and target MME. This can prevent the TAU process frombecoming complicated and reduce a signaling load.

First Modification of Fourth Embodiment

This modification discloses another configuration of the MME thatmanages the TAI of the mobile RN.

A plurality of MMES for mobile RN are provided. An MME for mobile RN maybe configured in a normal MME or a normal MME may be caused to functionalso as the MME for mobile RN. The functions of the MME for mobile RNmay be the functions disclosed in the fourth embodiment described above.

FIG. 32 is a diagram showing an architecture in a case where an MME formobile RN is configured in a normal MME. The configuration shown in FIG.32 is similar to the configuration shown in FIG. 13, and thus, thecorresponding parts are denoted by the same reference symbols and commondescription is omitted.

An m-MME for UE 3203 manages only a TA to which a mobile RN belongs. TheDeNB 1305 and m-MME for UE 3203 are connected by an S1 interface 3201.The m-MME for UE 3203 and S-GW for UE 1307 are connected by an S11interface 3202.

In this modification, the MME for UE 1302 and m-MME for UE 3203 areconfigured in the same MME 3200. Though different from the example shownin FIG. 32, the MME for RN 1301, MME for UE 1302, and m-MME for UE 3203may be configured in the same MME. In other words, there may beconfigured an MME that has the mobility management function of the RN,the mobility management function of the UE being served by the eNB,DeNB, or fixed RN, and the mobility function of the UE being served bythe mobile RN.

The MME for RN 1301 and m-MME for UE 3203 are connected by an interface3204. As a result, in a case where the RN has performed the TAU process,the MME for RN 1301 and m-MME for UE 3203 can exchange information.

In a case where the RN 1304 is a fixed RN and in a case where the RN1304 is a mobile RN and operates as a UE, the RN 1304 operates asdescribed with reference to FIG. 30.

In a case where the mobile RN 1304 operates as an eNB for UE,communications are performed among the UE 1303, mobile RN 1304, S1/X2proxy functionality of the DeNB 1305, m-MME for UE 3203, S-GW for UE1307, and P-GW for UE 1306. The operation in this case is also identicalto the operation described with reference to FIG. 30.

In the method disclosed in this modification, the TAI of the mobile RNand the TAIs of other cells such as eNB, DeNB, and fixed RN are notincluded in the same TAI list. If the TA to which the DeNB belongs isidentical to the TA to which the mobile RN belongs, they are notincluded in the same TAI list. An example of the above is a case inwhich the TAI of the mobile RN is made identical to the TAI of thetarget DeNB, which has been disclosed in the first embodiment.

FIG. 33 is a diagram for describing a TA to which a mobile RN belongsand a TA to which a UE being the mobile RN belongs in the firstmodification of the fourth embodiment. The configuration shown in FIG.33 is similar to the configuration shown in FIG. 15, and thus, thecorresponding parts are denoted by the same reference symbols and commondescription is omitted.

FIG. 33 shows a case in which an RN 3305 moves along an arrow 3300. Afirst m-MME 3301 is connected to all the DeNBs 1522 to 1527 connected tothe first MME 1520 by S1 interfaces 3303. A second m-MME 3302 isconnected to all the DeNBs 1502 to 1507 connected to the second MME 1501by S1 interfaces 3304.

The RN 3305 is located in a coverage 3307 provided by the RN 3305. A TAto which the RN 3305 before moving belongs is a fifth TA 3308. A UE 3306being served by the RN 3305 moves as the RN 3305 moves.

The RN 3305 before moving is connected to the sixth DeNB 1527. The sixthDeNB 1527 is connected to the first MME 1520 and the first m-MME 3301.The TA to which the RN 3305 before moving belongs is the fifth TA 3308.The fifth TA 3308 is managed by the first m-MME 3301.

After moving along the arrow 3300, the RN 3305 is connected to the tenthDeNB 1505. The tenth DeNB 1505 is connected to the second MME 1501 andthe second m-MME 3302. The TA to which the RN 3305 after moving belongsremains unchanged, which is the fifth TA 3308. The fifth TA 3308 aftermoving is managed by the second m-MME 3302.

The TAI list of the UE being served by the mobile RN and the TAI list ofthe UE being served by the fixed RN, eNB, or DeNB are managed bydifferent MMEs. The TAI list of the UE being served by the mobile RN ismanaged by the m-MME for UE. The TAI list of the UE being served by thefixed RN, eNB, or DeNB is managed by the MME for UE. Specificdescription is given with reference to FIG. 33.

The TAI list of the UE 3306 being served by the mobile RN 3305 beforemoving and the TAI lists of the UEs being served by first to sixth DeNBs1522 to 1527 are managed by different MMEs. Specifically, the TAI listof the UE 3306 being served by the mobile RN 3305 is managed by thefirst m-MME 3301 being an m-MME for UE. The TAI lists of the UEs beingserved by the first to sixth DeNBs 1522 to 1527 are managed by the firstMME 1520 being an MME for UE.

The TAI list of the UE 3306 being served by the mobile RN 3305 aftermoving and the TAI lists of the UEs being served by the seventh totwelfth DeNBs 1502 to 1507 are managed by different MMEs. Specifically,the TAI list of the UE 3306 being served by the mobile RN 3305 ismanaged by the second m-MME 3302 being an m-MME for UE. The TAI lists ofthe UEs being served by the seventh to twelfth DeNBs 1502 to 1507 aremanaged by the second MME 1501 being an MME for UE.

The TAI of the mobile RN and the TAI of the fixed RN, eNB, or DeNB arenot included in the same TAI list. The UE being served by the mobile RNattaches to the MME for mobile RN provided in the MME to which themobile RN has attached.

In a case where the mobile RN has performed inter-MME HO, the HO processand TAU process of the mobile RN are performed. The HO process and TAUprocess of the UE being served by the mobile RN are not performed.However, the TAU process of the UE is necessary. This is because the MMEis changed, and accordingly, the TA managed by the target MME differsfrom the TA managed by the source MME.

The methods disclosed in the first to third embodiments above can beused as the method of performing the TAU process of the UE. In thiscase, it suffices that the information is exchanged between the MME forRN and the m-MME for UE by means of the interface 3204 shown in FIG. 32.In a case where the UE manages the mobility between the mobile RN andthe eNB or DeNB, the TAU process is activated from the UE.

The method disclosed in this modification can avoid a situation in whichan m-MME needs to be connected to all DeNBs that support the mobile RN.It suffices that the m-MME is configured in a conventional MME to beconnected only to the DeNB that has been conventionally connected to theMME. Physical installation of an MME and connection of the MME to a DeNBare not newly required, making it easier to construct a communicationsystem, resulting in a reduction in the cost of constructing thecommunication system.

Second Modification of Fourth Embodiment

This modification discloses another configuration of the MME thatmanages the TAI of the mobile RN. The MME for mobile RN is configured ina predetermined DeNB, specifically, an MME to which a P-DeNB belongs.The MME to which the P-DeNB belongs may also function as the MME formobile RN.

The architecture in a case where the MME for mobile RN is included inthe MME to which the P-DeNB belongs can be configured similarly to thearchitecture shown in FIG. 13. However, the MME for UE 1302 in the MMEto which the P-DeNB belongs is provided with the function of the MME formobile RN. If all DeNBs can serve as a P-DeNB, it suffices to providethe function of the MME for mobile RN to the MMEs for UE in the MME towhich all the DeNBs belong.

In a case where the RN 1304 is a fixed RN and in a case where the RN1304 is a mobile RN and operates as a UE, the RN 1304 operates asdescribed with reference to FIG. 13.

In a case where the mobile RN 1304 operates as an eNB for a UE,communications are performed among the UE 1303, mobile RN 1304, S1/X2proxy functionality of the DeNB 1305, MME for UE 1302 to which thefunctions of the MME for mobile RN are added, S-GW for UE 1307, and P-GWfor UE 1306.

A Uu interface is used in the communication between the UE and mobileRN. An S1 interface is used in the communication between the mobile RNand m-MME for UE via the S1 proxy functionality of the DeNB. An S11interface is used in the communication between the m-MME for UE and S-GWfor UE. In a case where an X2 interface is used, the X2 interface isused in the communication between the mobile RN and neighbour eNB viathe X2 proxy functionality of the DeNB.

In the method disclosed in this modification, the TAI of the mobile RNand the TAI of the eNB or DeNB that belongs to the MME for the P-DeNBmay be included in the same TAI list.

FIG. 34 is a diagram for describing a TA to which a mobile RN belongsand a TA to which a UE being served by the mobile RN belongs in thesecond modification of the fourth embodiment. The configuration shown inFIG. 34 is similar to the configuration shown in FIG. 15, and thus, thecorresponding parts are denoted by the same reference symbols and commondescription is omitted.

The fourth DeNB 1525 is a P-DeNB. The first to twelfth DeNBs 1522 to1527 and 1505 to 1507 are DeNBs that support a mobile RN. The first MME1520 to which the P-DeNB 1525 belongs is connected to all the DeNBs 1522to 1527 and 1505 to 1507 by the S1 interfaces 1521 and S1 interfaces3405.

FIG. 34 shows a case in which an RN 3401 moves along an arrow 3400. TheRN 3401 is located in a coverage 3403 provided by the RN 3401. The TA towhich the RN 3401 before moving belongs is a fifth TA 3404. A UE 3402being served by the RN 3401 moves as the RN 3401 moves.

The RN 3401 before moving is connected to the P-DeNB 1525. The P-DeNB1525 is connected to the first MME 1520.

The RN 3401 moves along the arrow 3400 and is then connected to the DeNB1505. The DeNB 1505 is connected to the first MME 1520 and the secondMME 1501. The TA to which the RN 3401 after moving belongs remainsunchanged, which is the TA 3404. The TA 3404 is managed by the first MME1520.

The TAT list of the UE being served by the mobile RN and the TAI list ofthe UE being served by the fixed RN, eNB, or DeNB may be managed by thesame MME. Specifically, the TAI list of the UE being served by themobile RN and the TAI list of the UE being served by the fixed RN, eNB,or DeNB are managed by the MME for UE 1520 to be connected to theP-DeNB.

The TAI of the mobile RN and the TAI of the fixed RN, eNB, or DeNB maybe included in the same TAI list. The UE being served by the mobile RNattaches to the MME to be connected to the P-DeNB to which the mobile RNhas attached.

In a case where the mobile RN 3401 has performed inter-MME HO from theP-DeNB 1525 to the DeNB 1505, the HO process and TAU process of themobile RN 3401 are performed. However, the HO process and TAU process ofthe UE 3402 being served by the mobile RN 3401 are not performed. Themethod disclosed in this modification does not need the TAU process ofthe UE 3402 being served by the mobile RN.

This is because if the mobile RN 3401 performs inter-MME HO, the MMEthat manages the TAI of the UE 3402 being served by the RN 3401 is stillthe first MME 1520 and is not changed.

In a case where the UE has managed the mobility between the mobile RNand the fixed RN, eNB, or DeNB that has the same TAI as that of the RN,the TAU process from the UE is not activated.

The first MME 1520 for the P-DeNB 1525 for the mobile RN 3401 isconnected to all the DeNBs 1522 to 1527 and 1505 to 1507 that supportthe RN 3401. If the number of mobile RNs becomes enormous and eachP-DeNB is connected to a specific MME, the MME has difficulty inconnection with all the DeNBs that support the enormous number of mobileRNs. The method of solving this problem is disclosed below.

The mobile RNs are subjected to grouping. The DeNBs to be supported pergroup are limited. As a result, the DeNBs to be connected with the MMEcan be limited. Alternatively, a P-DeNB may be set for each of thegroups. The P-DeNB may be determined in advance per group. One or aplurality of P-DeNBs may be provided. Accordingly, the management of theTAIs can be unified for each of the groups, making it easy to maintainand manage the TAIs as a network, not limited to the MME.

Grouping of mobile RNs may be performed, for example, per service, suchas a group to be installed in a car of XX bullet train and a group to beinstalled in a car of YY bullet train.

The method disclosed in the fourth embodiment described above isapplicable as the method of taking a measure against the case in which aDeNB that supports a mobile RN is not connected to an MME to beconnected to a P-DeNB.

In the method disclosed in this modification, if a mobile RN performsinter-MME HO, the MME that manages the TAI of a UE being served by thisRN is not changed, whereby the UE does not need to perform the TAU. Thiscan solve the problem that a large number of TAUs occur simultaneously,which is caused by the methods disclosed in the first to thirdembodiments described above, eliminating the need for exchanging theinformation between the source MME and target MME. Thus, the TAU processcan be prevented from becoming complicated and a signaling load can bereduced.

The method disclosed in this modification can avoid a situation in whichthe MME needs to be connected to all DeNBs. It suffices that the MME tobe connected to the P-DeNB is connected to the DeNB within the movingrange of the mobile RN having the TAI of the P-DeNB. This makes it easyto construct a communication system, resulting in the cost ofconstructing the communication system.

Fifth Embodiment

When an RN has moved, some of the UEs being served by the RN movetogether with the RN and the others remain at the original locations.The MME has to recognize the UEs that have moved together with the RN.For example, in the method disclosed in the second embodiment describedabove, the RN notifies the MME for RN of the identity of the UE beingserved by the RN. Alternatively, in the method disclosed in the firstmodification of the second embodiment described above, the RN notifiesthe target MME for RN of the identity of the UE being served by the RN.The MME for RN notifies the MME for UE of the identity of this UE. Forthis notification, the RN or MME needs to recognize which UE has movedtogether with the RN. Specifically, the RN or MME needs to recognize theidentity of the UE that has moved together with the RN.

The RN recognizes the UE in the RRC_Connected state that is being servedby the own cell. The MME for UE recognizes a cell identity being anidentity of a serving cell for the UE in the RRC_Connected state,specifically, CGI or E-UTRAN cell global identifier (ECGI). In otherwords, the RN and MME for UE can recognize by which cell the UE in theRRC_Connected state is served.

In a case where the UE in the RRC_Connected state has moved, the RN andMME for UE can both judge whether the UE has moved outside of the cellthrough the HO process or remains in the cell. As a result, the RN cannotify the MME for RN of the identity of the UE being served by the RN,which has been disclosed in the second embodiment and the firstmodification of the second embodiment described above. Alternatively,the MME for UE may recognize and judge the identity of the UE beingserved by the RN.

However, the RN does not recognize the UE in the RRC_Idle state that isbeing served by the own cell. The MME cannot recognize by which cell theUE in the RRC_Idle state is served and can only recognize the abovewithin the range of the cell in the TAI list of the UE.

In a case where the UE in the RRC_Idle state has moved, the RN and MMEboth cannot judge whether the UE has moved outside of the cell orremains in the cell if the UE has moved within the cell range of the TAIlist of the UE.

In a case where the UE in the RRC_Idle state has moved together with theRN, the RN and MME cannot recognize this UE as described above. In otherwords, the RN and MME cannot recognize which UE in the RRC_Idle beingserved by the RN has moved together with this RN. Not only the targetMME but also the source MME cannot recognize which UE in the RRC_Idlestate being served by the RN has moved together with this RN.

Thus, the MME cannot notify the UE in the RRC_Idle state, which hasmoved together with the RN, of a paging signal, so that communicationbetween the UE and core network is not allowed.

This embodiment discloses the method of solving these problems. The TAIof the RN and the TAI of other type of cell, such as eNB and DeNB, areprohibited from being included in the same TAI list for UE. Even in acase where the same MME is connected to the eNB or DeNB and the RN, theTAI of the RN and the TAI of other type of cell are prohibited frombeing included in the same TAI list.

FIG. 35 is a diagram for describing cases in which a UE in the RRC_Idlestate moves and does not move together with a mobile RN. FIG. 35 shows acase in which an RN 3511 moves along an arrow 3500. FIG. 35(a) is adiagram showing a state of a mobile communication system before the RN3511 moves, and FIG. 35(b) is a diagram showing a state of the mobilecommunication system after the RN 3511 has moved.

A DeNB 3507 is located in a coverage 3514 provided by a first DeNB 3507.A first TA 3505 to which the first DeNB 3507 belongs is managed by afirst MME 3501. A second DeNB 3508 is located in a coverage 3516provided by the second DeNB 3508. A second TA 3506 to which the secondDeNB 3508 belongs is managed by a second MME 3502.

The first MME 3501 and first DeNB 3507 are connected by an S1 interface3503. The second MME 3502 and second DeNB 3508 are connected by an S1interface 3504. The RN 3511 is located in a coverage 3510 provided bythe RN 3511.

With reference to FIG. 35(a), a third TA 3509 to which the RN 3511before moving belongs is managed by the first MME 3501. A first UE 3512and a second UE 3513, which are both in the RRC_Idle state, are servedby the RN 3511.

With reference to FIG. 35(b), the TA to which the RN 3511 after movingbelongs is not changed from that before moving and is the third TA 3509.The third TA 3509 to which the RN 3511 after moving belongs is managedby the second MME 3502. The second UE 3513 remains at an originallocation and is in the RRC_Idle state to be served by the first DeNB3507. The first UE 3512 moves together with the RN 3511 and is in theRRC_Idle state to be served by the RN 3511.

The first UE 3512 that moves together with the RN 3511 is still beingserved by the RN 3511. Thus, the first UE 3512 judges that the TAI ofthe RN 3511 has already been located in the TAI of the own TA list anddoes not activate the TAU process. As a result, the first MME 3501recognizes that the UE is located in the cell within the TAI list of theUE.

Meanwhile, the second UE 3513 that does not move together with the RN3511 gets out of the coverage 3510 of the RN 3511, moves to the coverage3514 of the first DeNB 3507, and reselects the first DeNB 3507 as acell. The TAI of the DeNB and the TAI of the RN are prohibited frombeing included in the same TAI list, and thus, the TAI list of thesecond UE 3513 has no TAI of the first TA 3505 to which the first DeNB3507 belongs. The second UE 3513 accordingly activates the TAU processfor the first MME 3501. The TAU process of the second UE 3513 isperformed by the first MME 3501.

Thus, the first MME 3501 can recognize whether or not the second UE 3513that has not moved together with the RN 3511 and remained at itslocation is located in the TA managed by the own MME. Even if the DeNBto which the UE is connected varies and a cell is reselected between thedifferent MMEs, similarly, the target MME and source MME can bothrecognize whether or not this UE is located in the TA managed by the ownMME. The source MME and target MME can accordingly both recognize whichUE has remained at an original location or moved together with an RN.This allows for the UE to communicate with the core network.

Disclosed below is a specific example of the method in which an MMEavoids including the TAI of the RN and the TAI of other type of cell inthe same TAI list of the UE.

FIG. 36 is a diagram showing a sequence when an RN moves in a case wherethe TAI of the RN and the TAI of other type of cell are prohibited frombeing included in the same TAI list.

In Step ST3601, a first UE#1 is in the RRC_Idle state to be served bythe RN. In Step ST3602, a second UE#2 is in the RRC_Idle state to beserved by the RN.

In Step ST3603, the RN is RRC-connected to the first DeNB#1.

In Step ST3605, the MME for UE manages a TAI list_UE#1 being the TAIlist of the first UE#1 and a TAI list_UE#2 being the TAI list of thesecond UE#2. The TAI list_UE#1 includes a third TAI#3 being the TAI ofthe TA to which the RN belongs. Similarly, the TAI list_UE#2 includesthe third TAI#3. In Step ST3604, accordingly, the TAI list of the firstUE#1 includes the third TAI#3. In Step ST3606, the TAI list of thesecond UE#2 includes the third TAI#3.

In Step ST3607, the second UE#2 moves together with the RN. In StepST3608, the RN moves from being served by the first DeNB#1 to beingserved by the second DeNB#2. The first UE#1 remains at an originallocation.

In Step ST3609, the HO/TAU process is performed among the RN, firstDeNB#1, second DeNB#2, and MME for RN. In Step ST3610, the RN isRRC-connected to the second DeNB#2.

The first UE#1 remaining at the original location is being served by thefirst DeNB#1, and thus compares the first TAI#1 to which the firstDeNB#1 belongs and the TAI in the own TAI list and judges that the firstTAI#1 is not located.

In Step ST3611, the first UE#1 activates the TAU, whereby the TAUprocess of is performed among the first UE#1, first DeNB#1, and MME forUE. As a result, the MME for UE changes the TAI list_UE#1 of the firstUE#1. The TAI of the RN and the TAI of other type of cell are prohibitedfrom being included in the same TAI list, so that the MME for UE deletesthe third TAI#3 from the TAI list_UE#1 and includes the first TAI#1therein.

In Step ST3611, the MME for UE includes the updated TAI list_UE#1 in theTAU acceptance signal and then notifies the first UE #1 of the TAUacceptance signal. As a result, the first UE#1 updates the TAI list.

In Step ST3612, the TAI list of the first UE#1 includes only the firstTAI#1. In Step ST3613, the TAI list_UE#1 of the first UE#1 managed bythe MME for UE includes only the first TAI#1. Meanwhile, the TA to whichthe second UE#2 belongs remains unchanged, which is the third TAI#3, andthus, the MME for UE does not change the TAI list_UE#2.

In a case where the first UE#1 receives an incoming call in Step ST3614after moving of the RN, in Step ST3615, the MME for UE transmits apaging signal to the first DeNB#1 belonging to the first TAI#1 with theuse of the TAI list #UE1 of Step ST3613.

The first DeNB#1 checks the TAI list_UE#1 in the paging message. The TAIlist_UE#1 includes the first TAI#1 of the own cell, and thus, in StepST3616, the first DeNB#1 transmits the paging signal to the first UE#1being served thereby.

In a case where the second UE#2 receives an incoming call in Step ST3614after moving of the RN, the MME for UE transmits the paging signal tothe RN belonging to the third TAI#3 with the use of the TAI list #UE2 inStep ST3613. At that time, the RN is connected to the second DeNB#2, andthus, the MME for UE transmits the paging signal to the RN via thesecond DeNB#2 in Steps ST3617 and ST3618. When the RN moves, the DeNB tobe connected with the RN is changed in the HO/TAU process of the RN inStep ST3609. It suffices that the MME for UE obtains from the MME for RNthe information of the DeNB connected with the RN.

In Step ST3618, the second DeNB#2 that has received the paging messagefrom the MME for UE in Step ST3617 transmits this paging message to theRN by the proxy functionality. The RN that has received the pagingmessage checks the TAI list_UE#2 in the paging message. The TAIlist_UE#2 includes the third TAI#3 of the own cell, and thus, in StepST3619, transmits the paging signal to the second UE#2 being servedthereby.

In a case where the TAI list of the UE includes the TAI of the RN beforethe TAU process of the UE, if the TAI in which the UE is newly locatedis the TAI of the RN, the MME may add this TAI to the TAI list in theTAU process of the UE. In the TAU process of the UE, if the TAI whichnewly includes the UE is the TAI of other type of cell, the MME deletesthe TAI in the TAI list of the UE and includes the TAI of the other typeof cell in the TAI list.

Meanwhile, in a case where the TAI list of the UE includes the TAI ofother cell before the TAU process of the UE, if the TAI in which the UEis newly located is the TAI of the other cell, the MME may add this TAIto the TAI list in the TAU process of the UE. If the TAI in which the UEis newly located is the TAI of the RN in the TAU process of the UE, theMME deletes the TAI in the TAI list of the UE and includes the TAI ofthe RN in the TAI list.

Through the above, the MME can perform the incoming call process via thetarget DeNB for the UE or the RN even if the UE is in the RRC_Idlestate. The UE accordingly can communicate with the core network.

The MME is configured so as to judge whether the TAI is the TAI of theRN or the TAI of other cell. A specific example is disclosed below.

For example, in attach of the RN, the RN may notify the MME of theinformation indicating that the own cell is an RN. An operationadministration and maintenance (OAM) may notify the cell and the MME ofthe information indicating that the cell is an RN. The MME associatesthe information indicating that the cell is an RN with the identity ofthe cell being a target for this information, and manages the associatedones. The MME may notify the HSS of the information indicating that thecell is an RN. The HSS associates the information indicating that thecell is an RN and the identity of the cell being a target for theinformation and manages the associated ones. This enables the MME andHSS to recognize whether or not the cell is an RN, allowing formanagement as the RN.

The TAU request signal from the UE is notified the MME via the RN. TheRN notifies the MME of the TAU request signal from the UE, by includinga cell identity and TAI in the TAU request signal from the UE therein,or notifies the cell identity and TAI together with the TAU requestsignal. The MME can recognize whether or not the TAI belongs to the RNbased on the cell identity and the information indicating whether or nota cell to be associated with the cell identity is an RN. The MMEnotifies the HSS of the cell identity and the TAI, similarly, allowingthe HSS to recognize whether or not the TAI belongs to the RN.

As another example, the RN notifies the MME of the TAU request signalfrom the UE, by including the information indicating that the own cellis an RN, a cell identity, and TAI therein, or notifies the MME of theinformation above, a cell identity, and TAI together with the TAUrequest. This enables the MME to recognize whether or not the TAIbelongs to an RN. Not limited to the RN, but all the cells may transmitthe TAU request signal from the UE, by including the informationindicating whether the own cell is an RN or other type of cell, the cellidentity, and TA therein. This enables the MME to recognize whether theTAI belongs to the RN or belongs to other type of cell. Alternatively,the MME may notify the HSS of the cell identity and the TAI. Similarly,this enables the HSS to recognize whether or not the TAI belongs to theRN.

As another example, an RN notifies a UE being served thereby of theinformation indicating that the own cell is an RN. As the notificationmethod, the information may be notified a UE in dedicated signaling, forexample, RRC message or MAC message or may be broadcast as the systeminformation. The UE, which has received the information indicatingwhether or not the own cell is an RN, notifies the MME of the TAIrequest signal, by including the information indicating whether or notthe own cell is an RN therein, or notifies the MME of this informationtogether with a TAI request signal. This allows the MME to recognizewhether or not the TAI belongs to the RN, together with the cellidentity and TAI received from the RN. Not only the RN but also all thecells may notify UEs being served thereby of the information indicatingwhether or not the own cell is an RN or other type of cell. This allowsthe MME to recognize whether the TAI belongs to the RN or other type ofcell. Alternatively, the MME may notify the HSS of the cell identity andthe TAI. Similarly, this allows the HSS to recognize whether or not theTAI belongs to the RN.

The fixed RN and mobile RN may be operated separately such that only themobile RN is prohibited from being included in the same TAI list asother type of cell such as an eNB, DeNB, or fixed RN. Fixed and mobilemodes may be provided as RN modes. These modes allow the MME or HSS tojudge whether to forbid or permit to include the RN in the same TAI listas that of the other type of cell. The above-mentioned method isapplicable as the method in which the MME or HSS can recognize whetheror not the TAI is a TAI of a mobile RN or the TAI of other cell, orwhether the TAI is the TAI of the RN in the mobile mode or the TAI ofother cell. The information indicating whether or not an RN is a mobileRN or the information indicative of an RN mode may be used in place ofthe information indicating that the own cell is an RN.

In a case where TAIs of a plurality of mobile RNs are included in theTAI list of the UE, the MME cannot judge with which mobile RN the UE inthe RRC_Idle state has moved. Thus, TAIs of a plurality of mobile RNsmay be prohibited from being included in the same TAI list. As a result,the MME can recognize the UE even in a case where the UE in the RRC_Idlestate moves together with other mobile RN and is not served by theoriginal mobile RN.

First Modification of Fifth Embodiment

This modification discloses another method for solving the problemdescribed in the fifth embodiment. The MME manages two TAI lists for oneUE. The two TAI lists may be the TAI list for mobile RN and the TAI listfor other cell. A specific example thereof is disclosed below.

FIG. 37 is a diagram showing a sequence when the RN moves in a casewhere the MME manages two TAI lists for one UE.

In Step ST3701, a first UE#1 is in the RRC_Idle state to be served bythe RN. In Step ST3702, a second UE#2 is in the RRC_Idle state to beserved by the RN.

In Step ST3703, the RN is RRC-connected to the first DeNB#1.

In Step ST3705, an MME for UE manages two TAI lists for the first UE#1,specifically, a TAI list_UE#1 (RN) and a TAI list_UE#1 (other).Similarly, the MME for UE manages two TAI lists for the second UE#2,specifically, a TAI list_UE#2 (RN) and a TAI list_UE#2 (other).

The TAI list_UE#1 (RN) includes a third TAI#3 of a TA to which the RNbelongs. The TAI list_UE#1 (other) includes a first TAI#1 of a TA towhich a DeNB to be connected with the RN belongs.

Similarly, the TAI list_UE#2 (RN) includes the third TAI#3 of the TA towhich the RN belongs. The TAI list_UE#2 (other) includes the first TAI#1of the TA to which the DeNB to be connected with the RN belongs.

Thus, in Step ST3704, the TAI list_UE#1 of the first UE#1 includes thefirst TAI#1 and the third TAI#3. Similarly, in Step ST3706, the TAIlist_UE#2 of the second UE#2 includes the first TAI#1 and the thirdTAI#3.

In Step ST3707, the RN moves together with the second UE#2. In StepST3708, the RN moves from being served by the first DeNB#1 to beingserved by the second DeNB#2. The first UE#1 remains at the originallocation.

In Step ST3709, the HO/TAU process is performed among the RN, firstDeNB#1, second DeNB#2, and MME for RN. In Step ST3710, the RN isRRC-connected to the second DeNB#2.

The first UE#1 remaining at the original location is being served by thefirst DeNB#1, and thus, compares the first TAI#1 to which the firstDeNB#1 belongs with the TAI in the own TAI list and judges that thefirst TAI#1 is located. The first UE#1 accordingly does not activate theTAU.

The TAU process of the first UE#1 is not performed, and thus, the MMEfor UE does not change the TAI list_UE#1 (RN) and the TAI list_UE#1(other).

Meanwhile, the TA to which the second UE#2 belongs remains unchanged,which is the third TAI#3, and accordingly, the MME for UE does notchange the TAI list_UE#2 (RN) and the TAT list_UE#2 (other).

In a case where an incoming call is made to the first UE#1 in StepST3712 after moving of the RN, the MME for UE transmits a paging signalusing two TAI lists of the first UE#1 in Step ST3711, specifically, theTAI list_UE#1 (other) and TAI list_UE#1 (RN).

In Step ST3713, the MME for UE transmits the paging signal to the firstDeNB#1 belonging to the first TAI#1 included in the TAI list_UE#1(other).

In this case, the TAI in the TAI list_UE#1 (other) and the TAI in theTAI list_UE#1 (RN) are included together as the TAI list of the firstUE#1 in the paging message. Alternatively, two including the TAIlist_UE#1 (other) and TAI list_UE#1 (RN) may be included as the TAI listof the first UE#1 in the paging message. Still alternatively, the MMEmay judge to which cell being served thereby, which belongs to the TAIin the TAI list, the paging message is sent and may include only thisTAI list in a paging message to be transmitted to this cell.

Here, for example, in Step ST3713, a paging signal is transmitted to thefirst DeNB#1 that belongs to the first TAI#1 included in the TAIlist_UE#1 (other), and thus, only the TAT list_UE#1 (other) is includedin the paging message to be transmitted in Step ST3713.

The first DeNB#1 checks the TAI list of the first UE#1 in the pagingmessage. The TAI list of the first UE#1 includes the first TAI#1 of theown cell, and thus, the first DeNB#1 transmits the paging signal to thefirst UE#1 in Step ST3714.

In Steps ST3715 and ST3716, the MME for UE further transmits the pagingsignal also to the third TAI#3 included in the TAI list_UE#1 (RN). Inthis case, the TAI list to be included in the paging message is similarto the above.

The RN checks the TAI list of the first UE#1 in the paging message. TheTAI list of the first UE#1 includes the third TAI#3 of the own cell, andthus, the RN transmits the paging signal to the first UE#1 in StepST3717.

The second DeNB#2 proxies the paging message by the method disclosed inthe fifth embodiment described above. The first UE#1 is served by thefirst DeNB#1 and is not served by the RN, and accordingly, the firstUE#1 does not receive the paging signal from the RN in Step ST3717 butcan receive the paging signal from the first DeNB#1 in Step ST3714.

Meanwhile, in a case where an incoming call is made to the second UE#2in Step ST3712 after moving of the RN, the MME for UE transmits thepaging signal using two TAI lists of the second UE#2 in Step ST3711, theTAI list_UE#2 (other) and TAI list_UE#2 (RN).

As in the case of the first UE#1, in Step ST3718, the MME for UEtransmits the paging signal to the first DeNB#1 that belongs to thefirst TAW′ included in the TAI list_UE#2 (other). The first DeNB#1checks the TAI list of the second UE#2 in the paging message. The TAIlist of the second UE#2 includes the first TAI#1 of the own cell, andaccordingly, the first DeNB#1 transmits the paging signal to the secondUE#2 in Step ST3719.

In Steps ST3720 and ST3721, the MME for UE further transmits the pagingsignal also to the RN that belongs to the third TAI#3 included in theTAI list_UE#2 (RN).

The RN checks the TAI list of the second UE#2 in the paging message. TheTAI list of the second UE#2 includes the third TAI#3 of the own cell,and accordingly, the RN transmits the paging signal to the second UE#2in Step ST3722.

The second DeNB#2 proxies the paging message by the method disclosed inthe fifth embodiment described above. The second UE#2 is served by theRN and is not served by the first DeNB#1, and accordingly, the secondUE#2 does not receive the paging signal from the first DeNB#1 in StepST3719 but can receive the paging signal from the RN in Step ST3722.

As described above, the MME manages two TAI lists for one UE,specifically, the TAI list for mobile RN and the TAI list for othercell, and accordingly, the MME can perform an incoming call process viathe DeNB or RN to which the UE is connected even if the UE is in theRRC_Idle state. Thus, the UE can communicate with the core network.

Even if the TAI of the RN and the TAI of other cell are included in thesame TAI list, the MME is capable of performing an incoming call processvia the DeNB or RN to which the UE is connected. Thus, the UE cancommunicate with the core network.

The TAI of the RN and the TAI of other cell can be accordingly includedin the same TAI list, preventing a situation in which the UE repeatedlymoves between the RN and DeNB or between the neighbour eNBs and TAUsrepeatedly occur. This results in a reduction in signaling load.

As disclosed in FIG. 37, the UE does not need to recognize that thereare two TAI lists. Therefore, the operation of the UE does not need tobe changed from the conventional one. This can avoid control frombecoming complicated.

In the method disclosed in this modification, the MME always holds twoTAI lists for one UE and thus transmits a paging signal also to a cellin the TA including no UE. This results in an increase in signaling loadas a communication system.

Here, the method of deleting an unnecessary TAI list is disclosed. Oneof the TAI lists is deleted when a TAU occurs next or when the UEchanges to the RRC_Connected state. A specific example thereof isdisclosed below.

FIG. 38 is a diagram showing a sequence in which an MME deletes one ofthe TAI lists when a UE changes to the RRC_Connected state.

In Step ST3701, the first UE#1 is in the RRC_Idle state to be served bythe RN. In Step ST3702, the second UE#2 is in the RRC_Idle state to beserved by the RN.

In Step ST3710, the RN is RRC-connected to the second DeNB#2.

In Step ST3711, the MME for UE manages two TAI lists for the first UE#1,specifically, the TAI list_UE#1 (RN) and TAI list_UE#1 (other).Similarly, in Step ST3711, the MME for UE manages two TAI lists for thesecond UE#2, specifically, the TAI list_UE#2 (RN) and TAI list_UE#2(other).

The TAI list_UE#1 (RN) includes a third TAI#3 of a TA to which the RNbelongs. The TAI list_UE#1 (other) includes a first TAI#1 of a TA towhich the DeNB to be connected with the RN belongs.

Similarly, the TAI list_UE#2 (RN) includes the third TAI#3 of the TA towhich the RN belongs. The TAI list_UE#2 (other) includes the first TAW′of the TA to which the DeNB to be connected with the RN belongs.

Thus, in Step ST3704, the TAI list_UE#1 of the first UE#1 includes thefirst TAI#1 and third TAI#3. Similarly, in Step ST3706, the TAIlist_UE#2 of the second UE#2 includes the first TAI#1 and third TAI#3.

When starting communication, in order to notify the MME for UE of aservice request, in Step ST3802, the first UE#1 performs the process ofestablishing the RRC connection with the first DeNB#1, to thereby beingRRC-connected therewith. Then, the first UE#1 shifts to the RRCconnected state.

In Step ST3802, the first UE#1 that has changed to the RRC_connectedstate in Step ST3802 transmits a service request to the first DeNB#1. InStep ST3803, the first DeNB#1 transmits the service request to the MMEfor UE.

In Step ST3803, the first DeNB#1 includes at least any one of the cellidentity of the own cell and the TAT of the own cell in the servicerequest of the first UE#1. The MME for UE that has received the servicerequest recognizes that the first UE#1 is served by the first DeNB#1.This allows the MME for UE to recognize that the first UE#1 is notserved by the RN.

In Step ST3813, the MME for UE deletes or empties the TAI list_UE#1 (RN)of the first UE#1.

The TAI list of the first UE#1 has been changed, and accordingly, inSteps ST3805 and ST3804, the MME for UE transmits a TAI list updatemessage indicative of the updated TAI list to the first UE#1 via thefirst DeNB#1. In Steps ST3805 and ST3804, the MME for UE transmits theTAI list update message, by including the updated TAI list_UE#1 therein.The TAI list_UE#1 includes only the first TAI#1. This TAI list updatemessage may be S1 signaling.

The first UE#1 receives the TAU list update message in Step ST3804 and,in Step ST3806, updates the TAI included in the TAI list. Here, thethird TAI#3 is deleted and the first TAI#1 is left in the TAI list.

The case of the second UE#2 is disclosed, which is performed by a methodsimilar to that of the first UE#1.

When starting communication, in order to notify the MME for UE of aservice request, in Step ST3807, the second UE#2 performs the process ofestablishing RRC connection with the RN, to thereby being RRC connectedtherewith. Then, the second UE#2 changes to the RRC_Connected state.

In Step ST3807, the second UE#2 that has changed to the RRC_connectedstate in Step ST3807 transmits a service request to the RN. In StepST3808, the RN transmits the service request to the MME for UE.

In Step ST3808, the RN includes at least any one of the cell identity ofthe own cell and the TAT of the own cell in the service request of thesecond UE#2. The transmission from the RN to the MME for UE is performedvia the second DeNB#2, and the second DeNB#2 serves as a proxy to theMME for UE. The MME for UE that has received the service requestrecognizes that the second UE#2 is served by the RN. This allows the MMEfor UE to recognize that the second UE#2 is not served by the firstDeNB#1.

In Step ST3809, the MME for UE deletes or empties the TAI list_UE#2(other) of the second UE#2.

The TAI list of the first UE#2 has been changed, and accordingly, inSteps ST3810 and ST3811, the MME for UE transmits a TAI list updatemessage indicative of the updated TAI list to the second UE#2 via theRN. In Steps ST3810 and ST3811, the MME for UE transmits the TAI listupdate message, by including the updated TAI list_UE#2 therein. The TAIlist_UE#2 includes only the third TAI#3. This TAI list update messagemay be S1 signaling.

The transmission from the MME for UE to the RN is performed via thesecond DeNB#2, and the second DeNB#2 serves as a proxy to the RN. InStep ST3811, the second UE#2 receives a TAU list update message. InST3812, then, the second UE#2 updates the TAI included in the TAI list.In Step ST3812, the first TAI#1 is deleted and the third TAI#3 is leftin the TAI list.

As a result, the MME does not always hold two TAI lists for one UE andthus can prevent from transmitting a paging signal also to the cell inthe TA including no UE. This can prevent an increase in signaling loadas a communication system.

The TAI lists held by the MME for UE can be reduced as well, resultingin a reduction in storage capacity of the MME. This can reduce amanufacturing cost of an MME.

FIG. 38 shows the case in which the UE changes to the RRC connectedstate, which may be a case in which the UE activates the TAU, andsimilar effects can be achieved.

In Step ST3709 of FIG. 37, the MME for UE may recognize the TAI of theDeNB to be connected with the RN. In Step ST3709, the RN that has movedfrom the first DeNB#1 to the second DeNB#2 is subjected to the HOprocess and the TAU process. These processes allow the MME for RN torecognize that the RN has been connected to the second DeNB#2. The MMEfor RN and MME for UE are configured to exchange the informationregarding the DeNB connected with the RN, for example, the cell identityand a TAI to which the cell belong. This enables the MME for UE torecognize the TAI of the DeNB to be connected with the RN.

In Step ST3711, the MME for UE may update the TAI list of the UE. InStep ST3711, the MME for UE that has recognized the TAI of the DeNB tobe connected with the RN updates the TAI lists of the first UE#1 andsecond UE#2. The second TAI#2 is added to the TAI list_UE#1 (other) ofthe first UE#1. Also, the second TAI#2 is added to the TAI list_UE#2(other) of the second UE#2. The TAI list has been changed, andaccordingly, the MME for UE notifies the first UE#1 and the second UE#2of the updated TAI lists. The TAU list update method disclosed in FIG.38 may be used as the notification method.

As a result, as to the first UE#1 and second UE#2, the TAU list includesthe TAI of the second DeNB#2 to be connected with the RN. Thus, the UEthat has moved together with the RN does not need to generate a TAUprocess if it has moved between the DeNB and RN. This results in afurther reduction in signaling load.

In the method described above, the UE is required to have only one TAIlist and not required to have two TAI lists. However, the UE may havetwo TAI lists similarly to the TAI lists of the MME. In this case, theUE and MME can manage those as the same TAI list, reducing malfunctionsas much as possible in the operation of the TAI list.

Second Modification of Fifth Embodiment

This modification discloses another method for solving the problemdescribed in the fifth embodiment. The source MME and target MME bothhave or manage the TAI list for one UE. In a case where the source MMEis identical to the target MME, the MME may have and manage one TAI listof the UE.

Through the above, if the MME does not recognize whether or not a UE inthe RRC_Idle state has moved together with an RN, the source MME andtarget MME can both page the UE when an incoming call is made to the UE.Consequently, the UE can communicate with the core network. A specificexample thereof is disclosed below.

FIG. 39 is a diagram showing a sequence when an RN moves in a case wherethe source MME and target MME both manage the TAI list for one UE. FIG.39 shows the case in which the RN has performed inter-MME HO.

In Step ST3901, the first UE#1 is in the RRC_Idle state to be served bythe RN. In Step ST3902, the second UE#2 is in the RRC_Idle state to beserved by the RN.

In Step ST3903, the RN is RRC-connected to the first DeNB#1. In StepST3905, the first MME for UE is connected to the first DeNB#1. In StepST3905, the first MME for UE manages the TAI lists of the first UE#1 andsecond UE#2. The TAI list_UE#1 includes the third TAI#3 of a TA to whichthe RN belongs and a first TAM of a TA to which the first DeNB#1belongs. Similarly, the TAI list_UE#2 includes the third TAI#3 of the TAto which the RN belongs and first TAM of the TA to which the firstDeNB#1 belongs.

Thus, in Step ST3904, the TAI list_UE#1 of the first UE#1 includes thefirst TAI#1 and third TAI#3. Similarly, in Step ST3906, the TAIlist_UE#2 of the second UE#2 includes the first TAW′ and third TAI#3.

In Step ST3907, the second UE#2 moves together with the RN. In StepST3908, the RN moves from being served by the first DeNB#1 to beingserved by the second DeNB#2. The first UE#1 remains at an originallocation.

In Step ST3909, the HO/TAU process is performed among the RN, firstDeNB#1, second DeNB#2, first MME#1 for RN, and second MME#2 for RN. InStep ST3910, the RN is RRC-connected to the second DeNB#2.

The first UE#1 remaining at the original location is served by the firstDeNB#1, and thus compares the first TAI#1 to which the first DeNB#1belongs with the TAI of the own TAI list and judges that the first TAI#1is located. The first UE#1 accordingly does not activate the TAU.

The TAU process of the first UE#1 is not performed, and thus, the firstMME#1 for UE does not change the TAI list_UE#1.

Meanwhile, the TA to which the second UE#2 belongs remains unchanged,which is the third TAI#3, and thus, the first MME#1 for UE does notchange the TAI list_UE#2.

In Step ST3911, the first MME#1 for UE derives the UE including the TATof the RN that has moved in the TAI list.

It suffices that before performing the process of Step ST3911, the firstMME#1 for RN notifies the first MME#1 for UE of the TAI of the RN thathas moved.

Here, in Step ST3909, the first MME#1 for RN notifies the first MME#1for UE of the TAI of the RN that has moved. This enables the first MME#1for UE to recognize the TAI of the RN that has moved and to derive theUE including the TAI of the RN that has moved in the TAI list.

It suffices that in Step ST3909, the first MME#1 for RN notifies thefirst MME#1 for UE of the identity of the MME being the target for theRN that has moved. This allows the first MME#1 for UE to recognize theMME being the target for the RN that has moved.

The first MME#1 for UE detects that the TAI list_UE#1 and TAI list_UE#2include the third TAI#3 of the RN using the TAI list. The first MME#1for UE accordingly judges that the first UE#1 and second UE#2 includethe third TAI#3 of the RN.

In Step ST3912, the first MME#1 for UE notifies the second MME#2 for UEbeing the target for the RN of the TAI list of the UE together with theidentity of the derived UE. The first MME#1 for UE may notify the targetsecond MME#2 for RN of the TAI list of the UE together with the identityof the derived UE. It suffices that in that case, the target secondMME#2 for RN notifies the target second MME#2 for UE of thisinformation.

In Step ST3914, the second MME#2 for UE creates the TAI lists of thefirst UE#1 and second UE#2, specifically, the TAI list_UE#1 and TAIlist_UE#2. As a result, the TAI lists same as the TAI lists of the firstUE#1 and second UE#2 in the first MME#1 for UE are created on the secondMME#2 for UE.

In Step ST3913, the first MME#1 for UE continuously holds the TAI listsof the first UE#1 and second UE#2. As a result, the TAI lists of thefirst UE#1 and second UE#2 are possessed by both of the first MME#1 forUE and second MME#2 for UE.

Here, the first MME#1 for UE notifies the second MME#2 for UE being thetarget for the RN of the TAI list of the UE together with the identityof the derived UE. Alternatively, the second MME#2 for UE being thetarget for the RN may notify the source first MME#1 for UE of theinformation indicating that the notification of the TAI list of the UEis requested together with the identity of the derived UE. The firstMME#1 for UE that has received this information may notify the targetsecond MME#2 for UE of the TAI list of the UE together with the identityof the derived UE. In this case, the first MME#1 for UE may make anotification via the source first MME#1 for RN and the target secondMME#2 for RN.

The target MME may delete the TAI ineffective in the own MME from theTAI list of the UE. For example, in a case where the RN has performedinter-MME HO, in some cases, the target MME cannot manage the TA managedby the source MME. In such cases, the target MME deletes the TAIineffective in the own MME, and then, updates the TAI list of the UEwith the left TAI. Meanwhile, the TAI list of the UE in the source MMEis not changed and is left as it is.

Through the above, the TAI list of the UE that is managed by the targetMME is appropriately updated and does not include an unnecessary TA.This prevents the transmission of a paging signal also to an unnecessarycell, resulting in a reduction in signaling load.

FIG. 39 shows a case in which the second MME #2 deletes the TAI of theTA outside management of the own MME. In Step ST3915, the second MME#2for UE deletes the TAI of the TA outside management of the own MME. Thesecond MME#2 for UE deletes the first TAI#1 that is not managed by thesecond MME#2 for UE from the TAI lists of the first UE#1 and secondUE#2.

Consequently, in Step ST3916, the TAI list_UE#1 of the first UE#1includes only the third TAI#3 and the TAI list_UE#2 of the second UE#2includes only the third TAI#3. Here, the TAI lists of the first UE#1 andsecond UE#2 are changed in the second MME #2, which may be managed onlyin the MME and may be not notified to the UEs.

The UEs may be managed between the MME and HSS by the source MME andtarget MME. For example, the HSS has information per UE. The identity ofthe MME in which the UE is located is included in the information. Aplurality of identities may be included as the identity of the MME. Theidentity of the source MME and the identity of the target MME are bothheld (recorded) in the HSS as the identity of the MME in which the UE islocated, so that the HSS that has been requested the information of theUE can notify the identities of both of the source and target MMES. As aresult, the source and target MMES are both notified of an incoming callsignal when, for example, an incoming call is made. The source andtarget MMEs that have received the incoming call signal can both pagethe UE.

The UE does not recognize that the source MME and target MME eachinclude the TAI list. Therefore, only one TAI list is required in theUE.

In a case where an incoming call is made to the first UE#1 after movingof the RN, the HSS that has been requested the information of the firstUE#1 notifies the source node of the identities of the first MME #1 andsecond MME #2. Consequently, the MMEs of the first MME #1 and second MME#2 are notified of the incoming call signal to the first UE#1.

The first MME#1 for UE that has received the incoming call signal inStep ST3917 transmits a paging signal using the TAI list_UE#1 of thefirst UE#1 in Step ST3913. Specifically, in Step ST3918, the first MME#1for UE transmits the paging signal to the first DeNB#1 that belongs tothe first TAI#1 included in the TAI list_UE#1. The first DeNB#1 checksthe TAI list of the first UE#1 in the paging message. The TAI list ofthe first UE#1 includes the first TAI#1 of the own cell, and thus, inStep ST3919, the first DeNB#1 transmits the paging signal to the firstUE#1.

In Step ST3920, the first MME#1 for UE further transmits the pagingsignal also to the RN that belongs to the third TAI#3 included in theTAI list_UE#1. However, the RN has moved, and is thus not connected tothe first DeNB#1. Accordingly, the first DeNB#1 cannot proxy the pagingsignal to the RN. Therefore, the paging signal is not transmitted to theRN.

Meanwhile, the second MME#2 for UE that has received the incoming callsignal in Step ST3921 transmits the paging signal using the TAIlist_UE#1 of the first UE#1 in Step ST3916. Specifically, in StepST3922, the second MME#2 for UE transmits the paging signal to thesecond DeNB#2. In Step ST3923, the second DeNB#2 transmits the pagingsignal to the RN that belongs to the third TAI#3 included in the TAIlist_UE#1. The second DeNB#2 proxies the paging signal to the RN.

The RN checks the TAI list of the first UE#1 in the paging message. TheTAI list of the first UE#1 includes the third TAI#3 of the own cell, andthus, in Step ST3924, the RN transmits the paging signal to the firstUE#1.

The first UE#1 is served by the first DeNB#1 but is not served by theRN, and thus, the first UE#1 does not receive the paging signal from theRN in Step ST3924. The first UE#1 can receive the paging signal from thefirst DeNB#1 in Step ST3919.

Also in a case where an incoming call is made to the second UE#2 aftermoving of the RN, the HSS that has been requested the information of thesecond UE#2 notifies the source node of the identities of the first MME#1 and second MME #2, as in the case where an incoming call is made tothe first UE#1. As a result, the MMEs, the first MME #1 and second MME#2, are both notified of the incoming call signal to the second UE#2.

The first MME#1 for UE that has received the incoming call signal inStep ST3925 transmits a paging signal using the TAI list_UE#2 of thesecond UE#2 in Step ST3913. Specifically, in Step ST3926, the firstMME#1 for UE transmits a paging signal to the first DeNB#1 that belongsto the first TAI#1 included in the TAI list_UE#2. The first DeNB#1checks the TAI list of the second UE#2 in the paging message. The TAIlist of the second UE#2 includes the first TAI#1 of the own cell, andthus, the first DeNB#1 transmits the paging signal to the second UE#2 inStep ST3927.

In Step ST3928, the first MME#1 for UE further transmits the pagingsignal also to the RN that belongs to the third TAI#3 included in theTAI list_UE#2. However, the RN has been moved and is not connected tothe first DeNB#1, and thus, the first DeNB#1 cannot proxy the pagingsignal to the RN. Thus, the paging signal is not transmitted to the RN.

Meanwhile, the second MME#2 for UE that has received an incoming callsignal in Step ST3929 transmits a paging signal using the TAI list_UE#2of the second UE#2 in Step ST3916. Specifically, in Step ST3930, thesecond MME#2 for UE transmits the paging signal to the second DeNB#2. InStep ST3931, the second DeNB#2 transmits the paging signal to the RNthat belongs to the third TAI#3 included in the TAI list_UE#2. Thesecond DeNB#2 proxies the paging signal to the RN. The RN checks the TAIlist of the second UE#2 in the paging message. The TAI list of thesecond UE#2 includes the third TAI#3 of the own cell, and thus, in StepST3932, the second DeNB#2 transmits the paging signal to the secondUE#2.

The second UE#2 is served by the RN but is not served by the firstDeNB#1, and thus, the second UE#2 does not receive the paging signalfrom the first DeNB#1 in Step ST3927. The second UE#2 can receive thepaging signal from the RN in Step ST3932.

The method disclosed in this modification allows the MME to perform theincoming call process via a DeNB or RN to be connected with the UE evenif the UE is in the RRC_Idle state. The UE can accordingly communicatewith the core network.

Even if the TAI of the RN and the TAI of other cell are included in thesame TAI list, the MME can perform the incoming call process via theDeNB or RN to be connected with the UE. The UE can accordinglycommunicate with the core network.

The TAI of the RN and the TAI of other cell can be included in the sameTAI list, thereby preventing a situation in which the UE repeatedlymoves between the RN and DeNB or between neighbour eNBs and the TAUrepeatedly occurs. This results in a reduction in signaling load.

The UE does not need to recognize that there are two TAI lists. Thus,the operation of the UE is not required to be changed from theconventional one, avoiding control from becoming complicated. Also in acase where the RN performs inter-MME HO, the UE can communicate with thecore network.

The process of deleting the unnecessary TAI list of the MME is provided.In a case where the TAI list of the UE of any one of the source MME andtarget MME becomes unnecessary, the unnecessary TAI list of the UE ofone MME is deleted. The other TAI list is deleted when the TAU occursnext or when the UE next changes to the RRC_Connected state. Theunnecessary location information of the UE in the HSS may be deleted. Aspecific example thereof is disclosed below.

FIG. 40 is a diagram showing a sequence in which an MME deletes one TAIlist when the UE changes to the RRC_Connected state.

In Step ST3901, the first UE#1 is in the RRC_Idle state to be served bythe RN. In Step ST3902, the second UE#2 is in the RRC_Idle state to beserved by the RN.

In Step ST3910, the RN is RRC-connected to the second DeNB#2.

In Step ST3905, the first MME#1 for UE manages the TAI list_UE#1 of thefirst UE#1 and the TAI list_UE#2 of the second UE#2. The TAI list_UE#1includes a third TAI#3 of a TA to which the RN belongs and a first TAI#1of a TA to which the first DeNB#1 belongs. Similarly, the TAI list_UE#2includes the third TAI#3 and first TAI#1.

In Step ST3916, the second MME#2 for UE manages the TAI list_UE#1 of thefirst UE#1 and the TAI list_UE#2 of the second UE#2. The TAI list_UE#1includes the third TAI#3 of the TA to which the RN belongs. Similarly,the TAI list_UE#2 includes the third TAI#3.

In Step ST3904, the TAI list_UE#1 of the first UE#1 includes the firstTAI#1 and third TAI#3. Similarly, in Step ST3906, the TAI list_UE#2 ofthe second UE#2 includes the first TAM and third TAI#3.

When starting communication, in order to notify the MME for UE of aservice request, in Step ST4003, the second UE#2 performs the process ofestablishing RRC connection with the RN, to thereby being RRC-connectedtherewith. Then, the second UE#2 changes to the RRC_Connected state.

In Step ST4003, the second UE#2 that has changed to the RRC connectedstate in Step ST4003 transmits a service request to the RN. In StepST4004, the RN transmits a service request to the second MME#2 for UE.

In Step ST4004, the RN includes at least any one of the cell identity ofthe own cell and the TAI of the own cell in the service request of thesecond UE#2. The transmission from the RN to the second MME#2 for UE isperformed via the second DeNB#2, and the second DeNB#2 serves as a proxyto the second MME#2 for UE.

In Step ST4005, the second MME#2 for UE that has received the servicerequest judges that the second UE#2 is served by the RN. The secondMME#2 for UE accordingly recognizes that the second UE#2 is not servedby the first DeNB#1.

In Step ST4006, the second MME#2 for UE transmits, to the first MME#1for UE, a TAI list deletion request signal, specifically, a signal forrequesting the deletion of the TAI list_UE#2 of the second UE#2. Theinformation for requesting the deletion of a TAI list is included in theTAI list deletion request signal together with the identity (UE-ID) ofthe UE whose TAI list is deleted.

In Step ST4007, the first MME#1 for UE that has received the signal forrequesting the deletion of the TAI list_UE#2 deletes the TAI list_UE#2of the second UE#2. As a result, the TAI list of the second UE#2 isdeleted from the TAI lists in the first MME#1 for UE.

In Step ST4008, the TAI list_UE#1 of the first UE#1 is managed as it isin the first MME#1 for UE.

Next, the case of the first UE#1 is disclosed. A method similar to thatin the case of the second UE#2 is performed for the first UE#1.

When starting communication, in order to notify the first MME#1 for UEof a service request, in Step ST4010, the first UE#1 performs theprocess of establishing the RRC connection with the first DeNB#1, tothereby being RRC-connected therewith. Then, the first UE#1 changes tothe RRC_Connected state.

In Step ST4010, the first UE#1 that has changed to the RRC connectedstate in Step ST4010 transmits a service request to the first DeNB#1. InStep ST4009, the first DeNB#1 transmits the service request to the firstMME#1 for UE.

In Step ST4009, the first DeNB#1 includes at least any one of the cellidentity of the own cell and the TAI of the own cell in the servicerequest of the first UE#1. In Step ST4011, the first MME#1 for UE thathas received the service request judges that the first UE#1 is served bythe first DeNB#1. The first MME#1 for UE accordingly recognizes that thefirst UE#1 is not served by the RN.

In Step ST4012, the first MME#1 for UE transmits, to the second MME#2for UE, a TAI list deletion request signal, specifically, a signal forrequesting the deletion of the TAI list_UE#1 of the first UE#1. Theinformation for requesting the deletion of a TAI list is included in theTAI list deletion request signal together with the identity (UE-ID) ofthe UE whose TAT list is deleted.

In Step ST4013, the second MME#2 for UE that has received the signal forrequesting the deletion of the TAI list_UE#1 deletes the TAI list_UE#1of the first UE#1. As a result, the TAI list of the first UE#1 isdeleted from the TAI lists in the second MME#2 for UE.

In Step ST4014, the TAI list_UE#2 of the second UE#2 is managed as it isin the second MME#2 for UE.

The TAI list of the first UE#1 is not changed in the first MME#1 for UE,and thus, the first MME#1 for UE does not need to transmit the updatedTAI list to the first UE#1.

The TAI list of the second UE#2 is changed in the second MME#2 for UE,and thus, in Step ST4015, the second MME#2 for UE transmits the updatedTAI list to the RN via the second DeNB#2.

In Step ST4016, the RN transmits the updated TAI list to the secondUE#2. In the sequence shown in FIG. 40, in Steps ST4015 and ST4016, theupdated TAI list_UE#2 is included in a TAI list update message and thenis transmitted. The TAI list_UE#2 includes only the third TAI#3. The TAIlist update message may be S1 signaling.

In Step ST4017, the second UE#2 that has received the TAU list updatemessage in Step ST4016 updates a TAI included in the TAI list. In StepST4017, the first TAI#1 is deleted and the third TAI#3 is left in theTAI list.

The method of deleting the unnecessary location information of the UE inthe HSS is disclosed.

With reference to FIG. 40, the first MME#1 for UE notifies the HSS ofthe identity of the own MME, the identity of the second UE#2 whoselocation information is deleted, and the information indicating that thefirst MME #1 is deleted from the location information of the second UE#2in the HSS for the UE. The HSS that has received this informationdeletes the location information of the first MME #1 from the locationinformation of the second UE#2.

Similarly, the second MME#2 for UE notifies the HSS of the identity ofthe own MME, the identity of the first UE#1 whose location informationis deleted, and the information indicating that the second MME #2 isdeleted from the location information of the first UE#1 in the HSS forthe UE. The HSS that has received this information deletes the locationinformation of the second MME #2 from the location information of thefirst UE#1.

The unnecessary TAI list of the MME and location information in the HSSare deleted, which avoids the MME and HSS from continuously holding theunnecessary information, resulting in a reduction in unnecessary pagingto a cell. This can reduce a signaling load. Also, the storagecapacities of the MME and HSS can be reduced. This results in reductionsin manufacturing costs of the MME and HSS.

Third Modification of Fifth Embodiment

This modification discloses another method for solving the problemdescribed in the fifth embodiment. After moving, the RN performs pollingon the UEs to be served thereby, which are in the RRC_Idle state. Theinformation for polling may be provided to the system information. Theinformation for polling may be a minimum information amount, one bit.For example, polling is necessary when the information for polling is“1” or polling is not necessary when the information for polling is “0”.

The RN sets the information for polling in the system information to “1”and broadcasts this. In a case where the information for polling ischanged from “0” to “1”, the RN performs, on the UE being servedthereby, the process of correcting the system information. The RNnotifies the UE being served thereby that the system information hasbeen corrected through paging. Then, the RN broadcasts, to the UE beingserved thereby, the changed information for polling “1” as the systeminformation. The UE recognizes that the system information has beencorrected through paging and receives the system information to bebroadcast. As a result, the UE in the RRC_Idle state can receive thechanged information for polling.

In the case where the information for polling is “1”, the UE that hasreceived the broadcast information and obtained the information forpolling recognizes that polling is necessary and transmits a signalindicative of its presence to the RN. In the case where the informationfor polling is “0”, the UE does nothing. A random access procedure maybe activated as the method in which a UE transmits a signal indicativeof its presence to the RN. The RN that has received a random accesssignal through the random access procedure recognizes that the UE isserved thereby.

In finishing polling, the RN sets the information for polling to “0” andbroadcasts this. The method of notifying the UEs being served thereby issimilar to that in a case where the RN performs polling.

The RN may perform polling on the UEs to be served thereby, which are inthe RRC_Connected state. Polling may be performed for connectionconfirmation. For example, it can be checked whether or not an equipmentor the like performing the DRX operation has not moved to other cellduring DRX. The method disclosed in this modification is also applicableto the polling on the UEs in the RRC_Connected state.

Examples of the case in which the RN activates polling may include acase in which the RN has completed the HO process, a case in which theRN has completed the connection with a target DeNB, a case in which theRN has transmitted a HO confirm signal to the target MME, a case inwhich the RN transmits a TAU request signal to a target MME, and a casein which the RN transmits a TAU completion signal to a target MME.

As the case in which the RN ends polling, it suffices that apredetermined period has elapsed after the activation of polling.Alternatively, it suffices that a predetermined period has elapsed afterthe execution of the process of correcting the system information by theRN. The predetermined period may be determined in advance. Thepredetermined period may be managed by a timer.

As another method in which an RN performs polling, the information forpolling may be included in the paging message. Paging allows the RN tonotify the UE being served thereby of the information for polling. Thesystem information does not need to be changed unlike theabove-mentioned method, simplifying control of the RN and UE.

After moving of the RN, the target MME for RN or target MME for UE mayperform polling on UEs being served by the RN, which are in the RRC_Idlestate, via the RN that has moved. Alternatively, the source MME for RNor source MME for UE may perform polling on UEs being served by theDeNB, which are in the RRC_Idle state, via the DeNB to which the RN hasbeen connected before moving.

As the method in which the MME performs polling, a paging message may beused. The information for polling may be provided in the paging message.The information for polling may be a minimum information amount, onebit. For example, polling is necessary in a case where the informationfor polling is “1”, or polling is not necessary in a case where theinformation for polling is “0”.

The MME sets the information for polling in the paging message to “1”and notifies the UE of this via the RN. In the case where theinformation for polling is “1”, the UE that has received the pagingmessage and obtained the information for polling recognizes that pollingis necessary, and transmits a signal indicative of its presence to theMME via the RN. In the case where the information for polling is “0”,the UE does nothing. As the method in which the UE transmits a signalindicative of its presence to the MME, the UE may transmit an initial UEmessage. In this case, the RN may include the cell identity of the ownRN in the initial UE message and then transmits the initial UE messageto the MME. The MME that has received the initial UE message via the RNrecognizes that a UE is served by the RN.

As a result, the RN or MME can recognize whether or not the UE in theRRC_Idle state has moved together with the RN. Accordingly, in a casewhere an incoming call is made to the UE, the source MME and target MMEcan both page the UE. This allows the UE to communicate with the corenetwork.

The methods disclosed in the fifth embodiment to the third modificationof the fifth embodiment described above and the method disclosed in thesecond embodiment or the first modification of the second embodimentdescribed above may be used in combination. The MME can manage themobility of the UE being served by the RN if the UE being served by theRN is in the RRC_Connected state or RRC_Idle state. The communicationbetween the UE and core network is accordingly allowed.

For example, in a case where the method disclosed in the fifthembodiment described above and the method disclosed in the secondembodiment or the first modification of the second embodiment describedabove are used in combination, as to the UE being served by the RN,which is in the RRC_Connected state, the method disclosed in the secondembodiment or the first modification of the second embodiment describedabove may be applied in the HO/TAU process of the RN in Step ST3609 ofFIG. 36.

Sixth Embodiment

The first modification of the second embodiment above has disclosed themethod of transmitting and receiving the information regarding a UEbetween a target MME and a source MME. The information regarding a UEbeing served by the RN is transmitted and received between the sourceMME and target MME, and thus, the method of activating the TAU processof the UE is disclosed.

Here, another method is disclosed.

In the TAU process of the RN, the transmission and reception of theinformation regarding a UE being served by an RN as well as thetransmission and reception of the information regarding the RN areperformed between the source MME and target MME. A specific example ofthe TAU process of the RN in this embodiment is disclosed below.

FIG. 41 is a diagram showing a sequence in a case where in the TAUprocess of the RN, the transmission and reception of the informationregarding a UE being served by an RN as well as the transmission andreception of the information regarding the RN are performed between thesource MME and target MME. The sequence shown in FIG. 41 is similar tothe sequence shown in FIG. 27, and thus, the same steps are denoted bythe same step numbers, and common description is omitted.

In Step ST2701, the RN activates the TAU and transmits a TAU requestsignal to the target MME for RN.

The RN transmits the identity of a UE being served by the RN to thetarget MME for RN together with the TAU request signal. Further, the RNmay transmit the identity of the RN together.

After receiving the TAU request signal from the RN in Step ST2701, thetarget MME for RN performs the TAU process of the RN.

In Step ST2704, the target MME for RN transmits a context request signalto the source MME for RN. At this time, the target MME for RN transmitsthe identity of the UE being served by the RN, and further, the identityof the RN together.

Upon receipt of the context request signal in Step ST2704, in StepST4101, the source MME for RN transmits the context request signal ofthe UE being served by the RN to the source MME for UE. At this time,the source MME for RN transmits the identity of the UE being served bythe RN, and further, the identity of the RN together.

In Step ST4102, the source MME for UE transmits the context informationof the UE being served by the RN to the source MME for RN in response tothe context request signal of the UE being served by the RN that hasbeen received in Step ST4101.

In Step ST4103, the source MME for RN that has received the contextinformation of the UE being served by the RN transmits a contextinformation acceptance success signal of a UE being served by an RN tothe source MME for UE.

In Step ST4104, the source MME for RN that has received the contextinformation of the UE being served by the RN transmits, to the targetMME for RN, the context information of the UE being served by the RNtogether with the context information of the RN.

In Step ST4105, the target MME for RN, which has received the contextinformation of the UE being served by the RN together with the contextinformation of the RN, transmits the context information acceptancesuccess signal of the RN and the UE being served by the RN to the sourceMME for RN.

In Step ST4106, the target MME for RN, which has received the contextinformation of the UE being served by the RN together with the contextinformation of the RN, transmits the context information of the UE beingserved by the RN to the target MME for UE. The target MME for RNtransmits location update activation request information of a UE beingserved by an RN, together with the context information. At this time,the identity of the UE being served by the RN may be transmittedtogether. The RN identity may be transmitted together.

In Steps ST2710, ST2712, ST2714, and ST2716, the target MME for RN thathas transmitted the context information acceptance success signal of theRN and the UE being served by the RN in Step ST4105 performs the processof updating the location of the RN.

In Steps ST2711, ST2713, ST2715, and ST2717, the target MME for UE thathas received the location update activation request signal of the UEbeing served by the RN in Step ST4106 performs the process of updatingthe location of the UE being served by the RN.

After the process of updating the location of the UE being served by theRN, in Step ST4107, the target MME for UE notifies the target MME for RNthat the process of updating the location of the UE being served by theRN has been completed.

In Step ST2718, the target MME for RN transmits a TAU acceptance signalto the RN. In Step ST2720, the RN transmits a TAU completion signal tothe target MME for RN. Through the above, the TAU processes of the RNhave been completed in order.

The transmission of the TAU acceptance signal and the transmission ofthe TAU completion signal in Steps ST2719 and ST2721 are performed onlyin a case where there is information to be transmitted to the UE. Notthe TAU acceptance signal but other S1 signaling may be used.

As disclosed in this embodiment, in the TAU process of the RN, thetransmission and reception of the information regarding the UE beingserved by the RN as well as the transmission and reception of theinformation regarding the RN are performed between the source MME andtarget MME, so that the process equal to the TAU process of the UE beingserved by the RN is performed.

The source MME and target MME can accordingly recognize that the UEbeing served by the RN has moved, and can manage the mobility. Thisallows the target MME to configure and manage the TAI list of the UE,allowing for communication between the UE and core network.

The transmission and reception of the information regarding the UE beingserved by the RN as well as the transmission and reception of theinformation regarding the RN are performed, resulting in a reduction insignaling load between the source MME and target MME.

First Modification of Sixth Embodiment

The sixth embodiment above has disclosed that the transmission andreception of information regarding a UE being served by an RN as well asthe transmission and reception of the information regarding the RN areperformed between the source MME and target MME in the TAU process ofthe RN. In this modification, the process of updating the location ofthe UE being served by the RN as well as the process of updating thelocation of the RN is performed. A specific example of the TAU processof the RN in this modification is disclosed below.

FIG. 42 is a diagram showing a sequence in a case where the locationupdate process of the RN and the location update process of the UE beingserved by the RN are both performed in the TAU process of the RN. Thesequence shown in FIG. 42 is similar to the sequence shown in FIG. 41,and thus, the same steps are denoted by the same step numbers and commondescription is omitted.

In Step ST4201, the target MME for RN that has received the contextinformation of the UE being served by the RN together with the contextinformation of the RN in Step ST4104 transmits the context informationof the UE being served by the RN to the target MME for UE. At this time,the identity of the UE being served by the RN is transmitted together.The identity of the RN may be transmitted together.

In Step ST4202, the target MME for RN, which has transmitted the contextinformation acceptance success signal of the RN and the UE being servedby the RN in Step ST4105, transmits a location update request signal tothe HSS. The information for requesting location update of the RN andthe information for requesting location update of the UE being served bythe RN are included in the location update request signal. At this time,the identity of the RN and the identity of the UE being served by the RNare transmitted together.

The HSS that has received the location update request signal in StepST4202 performs the process of updating the location of the RN and theprocess of updating the UE being served by the RN.

In Step ST4203, the HSS transmits, to the source MME for RN, a locationcancellation request signal for requesting a location cancellation. Theinformation for requesting a location cancellation of the RN and theinformation for requesting a location cancellation of the UE beingserved by the RN are included in the location cancellation requestsignal. At this time, the identity of the RN and the identity of the UEbeing served by the RN may be transmitted together.

The source MME for RN that has received the location cancellationrequest signal cancels the location of the RN. In Step ST4204, thesource MME for RN further transmits a signal for requesting the locationcancellation of a UE being served by the RN to the source MME for UE. Atthis time, the identity of the UE being served by the RN may betransmitted together. The RN identity may be transmitted together.

The source MME for UE that has received the location cancellationrequest signal of the UE being served by the RN cancels the location ofthe UE being served by the RN.

In Step ST4205, the source MME for UE transmits a location cancellationcompletion signal of the UE being served by the RN to the source MME forRN.

In Step ST4206, the source MME for RN, which has recognized that thelocation of the RN had been cancelled and the location of the UE beingserved by the RN had been cancelled, notifies the HSS that thecancellations of the locations of the RN and the UE being served by theRN have been completed.

The HSS performs the process of updating the location of the RN and theprocess of updating the location of the UE being served by the RN. InStep ST4207, the HSS, which has recognized that the locations of the RNand the UE being served by the RN had been canceled, notifies the targetMME for RN of a location update completion signal of the RN and the UEbeing served by the RN.

In Step ST4208, the target MME for RN that has received the locationupdate completion signal notifies the target MME for UE that thelocation update of the UE being served by the RN has been completed.

Through the above, the location update process of the RN and thelocation update process of the UE being served by the RN can beperformed in the TAU process of the RN.

As a result, signalings can be reduced between the HSS and the sourceMME and between the HSS and the target MME. The signaling load in themobility management of the UE being served by the RN can be preventedfrom increasing.

In Step ST4209, the target MME for RN transmits a TAU acceptance signalto the RN. Included in the TAU acceptance signal are the informationindicative of the TAU accept of the RN and the information indicatingthat the TAU process of the UE being served by the RN has beenperformed, namely indicating that the context has been forwarded and thelocation information has been updated and the old location informationhas been canceled. At this time, the identity of the UE being served bythe RN is transmitted together.

In Step ST4210, the RN transmits, to the UE being served thereby, theinformation indicating that the TAU process of the UE has beenperformed. FIG. 42 shows this transmitted signal as a TAU acceptancesignal.

In Step ST4211, the UE being served by the RN receives the informationindicating that the TAU process has been performed and notifies the RNthat the TAU process, for example, a change of the TAI list, has beencompleted in the UE.

In Step ST4212, the RN transmits the information indicating that the TAUprocess of the UE being served thereby has been completed to the targetMME for RN, together with the completion of the TAU process of the RN.

The processes of Steps ST4210 and ST4211 may be performed only in a casewhere there is information to be transmitted to the UE. The method ofmaking a notification from the RN to the UE, which has been disclosed inthe first modification of the second embodiment described above, isapplicable to the notification from the RN to the UE. The notificationfrom the UE to the RN may be performed through dedicated signaling. Forthe UE in the RRC_Idle state, it suffices that the process ofestablishing the RRC connection with the RN is performed and anotification is made through dedicated signaling after the UE shifts tothe RRC connected state.

As described above, a part of the process in a case where there isinformation to be transmitted to the UE is included in the TAUacceptance signal of the RN, resulting in a simplification of theprocess. This reduces a signaling amount on the core network side withrespect to the RN.

The method disclosed in this modification can suppress an increase insignaling load in the mobility management of a UE being served by an RN.

Seventh Embodiment

This embodiment discloses another method for solving a problem that whenan RN moves, a source MME and a target MME cannot recognize a UE beingserved by the RN and the communication between the UE and core networkis not allowed.

In a case where the RN has performed the HO process, the RN transmits,to the UE being served thereby, a signal to request the activation ofthe TAU.

The following two methods are disclosed as specific examples of the casein which an RN notifies a UE being served thereby of a TAU activationrequest signal.

(1) Case in which an RN transmits a TAU request.

(2) Case in which an RN receives a TAU accept.

The method (1) above is suitable for a case in which a related node hasa high capability enough to simultaneously perform the TAU process of anRN and the TAU process of a UE being served by the RN. The TAU processof the RN and the TAU process of the UE being served by the RN aresimultaneously performed, resulting in a reduction in process delay.

The method (2) above is suitable for a case in which a related nodecannot simultaneously perform the TAU process of an RN and the TAUprocess of a UE being served by the RN. The method (2) above is alsoapplicable to a case in which a related node has low processingcapability.

Disclosed below is a specific example of the method in which an RNrequests a UE being served thereby to activate the TAU in a case wherethe RN has performed the HO process.

FIG. 43 is a diagram showing a sequence in which an RN notifies a UEbeing served thereby of a TAU activation request signal in a case wherethe RN performs the HO process. The sequence shown in FIG. 43 is similarto the sequence shown in FIG. 26, and thus, the same steps are denotedby the same step numbers and common description is omitted. FIG. 43shows a case of inter-MME HO.

In Step ST4301, the RN that has moved transmits a TAU request signal tothe target MME for RN. In Step ST4303, accordingly, the TAU process ofthe RN is performed among the RN, source DeNB, target DeNB, source MMEfor RN, target MME for RN, and HSS.

In Step ST4302, the RN transmits a TAU activation request signal to theUE being served thereby, triggered by the TAU request signal transmittedfrom the RN to the target MME for RN. The method of making anotification from the RN to the UE, which has been disclosed in thefirst modification of the second embodiment described above, isapplicable to the transmission of the TAU activation request signal.

In Step ST4304, the UE that has received the TAU activation requestsignal from the RN activates the TAU process. In Step ST4304, the UEtransmits the TAU request signal to an MME to be connected to a DeNBthat serves the RN after moving, specifically, the target MME for UE.Upon this, the TAU process of the UE is performed among the UE, RN,source DeNB, target DeNB, source MME for UE, target MME for UE, sourceS-GW for UE, target S-GW for UE, P-GW for UE, and HSS.

The method disclosed in this embodiment causes the RN to move and thenperform the TAU process and causes the UE being served by the RN thathas moved together therewith to activate the TAU process as well. Thetarget MME and source MME can accordingly manage the UE mobility,allowing for communication between the UE and core network.

The method disclosed in this embodiment is applicable not only to a casein which the RN performs inter-MME HO but also to a case in which the RNperforms intra-MME HO. The use of the method of this embodiment allowsfor application of the same procedure irrespective of whether HO isinter-MME HO or intra-MME HO. This can simplify the control for allowingcommunication between a UE being served by an RN and a core network.

Eighth Embodiment

This embodiment discloses another method for solving a problem that whenan RN moves, a source MME and a target MME cannot recognize a UE beingserved by the RN and communication between the UE and core network isnot allowed.

The seventh embodiment described above is configured such that when anRN performs a HO process, the RN transmits, to a UE being servedthereby, a signal to request the activation of the TAU. In thisembodiment, meanwhile, the core network transmits, to the UE beingserved by the RN that has moved, a signal to request the activation ofthe TAU. The core network may be an MME for RN. The core network may bean MME for UE, S-GW for UE, or HSS, not limited to the MME for RN.Alternatively, the core network may be an S-GW functionality of a sourceDeNB. In a case where the RN performs inter-MME HO, it suffices that thecore network is a target MME.

The following two methods are disclosed as specific examples of the casein which an MME for RN notifies a UE being served by an RN of a TAUactivation request signal.

(1) Case in which the MME for RN receives a TAU request from the RN.

(2) Case in which the MME for RN transmits a TAU accept to the RN.

The method (1) above is suitable for a case in which a related node hasa high capability enough to simultaneously perform the TAU process of anRN and the TAU process of a UE being served by the RN. The TAU processof the RN and the TAU process of the UE being served by the RN aresimultaneously performed, resulting in a reduction in process delay.

The method (2) above is suitable for a case in which a related nodecannot simultaneously perform the TAU process of an RN and the TAUprocess of a UE being served by the RN. The method (2) above is alsoapplicable to a case in which a related node has low processingcapability.

Disclosed below is a specific example of the method in which an MME forRN requests a UE being served by an RN to activate the TAU in a casewhere the RN performs the HO process.

FIG. 44 is a diagram showing a sequence in which an MME for RN notifiesa UE being served by an RN of a TAU activation request signal in a casewhere the RN performs the HO process. The sequence shown in FIG. 44 issimilar to the sequence shown in FIG. 26, and thus, the same steps aredenoted by the same step numbers and common description is omitted. FIG.44 shows a case of inter-MME HO.

In Step ST4401, the RN that has moved transmits a TAU request signal tothe target MME for RN. Upon this, in Step ST4402, the TAU process of theRN is performed among the RN, source DeNB, target DeNB, source MME forRN, target MME for RN, and HSS.

In Step ST4403, the target MME for RN transmits a TAU acceptance signalto the RN. The target MME for RN includes the information to request theUE being served by the RN to activate the TAU in the TAU acceptancesignal. At this time, the identity of the UE being served by the RN istransmitted together.

The TAU acceptance signal, which includes the information to request theUE being served by the RN to activate the TAU, is transmitted in StepST4403, not limited to the above. Alternatively, other S1 signaling maybe used or a signal for requesting a UE being served by the RN toactivate the TAU may be newly provided and transmitted.

In Step ST4404, the RN transmits a TAU activation request signal to a UEbeing served thereby based on the information to request the UE beingserved by the RN to activate the TAU, which has been received from thetarget MME for RN. The method of making a notification from the RN tothe UE, which has been disclosed in the first modification of the secondembodiment described above, is applicable to the transmission of the TAUactivation request signal.

The target MME for RN may transmit, to the RN via the target MME for UE,a signal on which the information to request a UE being served by the RNto activate the TAU is mapped. Alternatively, the target MME for RN maytransmit, to the target MME for UE and to a UE being served by an RN viathe RN, a signal on which the information to request the activation ofthe TAU is mapped.

In Step ST4405, the UE that has received the TAU activation requestsignal from the RN activates the TAU process. In Step ST4404, the UEtransmits a TAU request signal to an MME to be connected to a DeNB thatserves the RN after moving, specifically, the target MME for UE. Uponthis, the TAU process of the UE is performed among the UE, RN, sourceDeNB, target DeNB, source MME for UE, target MME for UE, source S-GW forUE, target S-GW for UE, P-GW for UE, and HSS.

The method disclosed in this embodiment causes the RN to move and thenperform the TAU process and causes the UE being served by the RN thathas moved together therewith to activate the TAU process. The target MMEand source MME can accordingly manage the UE mobility, allowing forcommunication between the UE and core network.

The method disclosed in this embodiment is applicable not only to thecase in which the RN performs inter-MME HO but also to the case in whichthe RN performs intra-MME HO. The use of the method of this embodimentallows for application of the same procedure irrespective of whether HOis inter-MME HO or intra-MME HO. This can simplify the control forallowing communication between a UE being served by an RN and a corenetwork.

Ninth Embodiment

In a case where a large number of UEs being served by an RNsimultaneously activate the TAU and the TAU processes of the largenumber of UEs are performed simultaneously, signaling loads mayconcentrate on the core network side with respect to the RN, and thus, acontrol delay and a TAU process failure may occur. Examples of the aboveare the cases disclosed in the first embodiment, seventh embodiment, andeighth embodiment described above. Examples of the above include a casein which the TAI of the RN is changed and a case in which the RN or thecore network side requests the TAU from the UE being served by the RN.In order to solve such a problem, the TAU processes of the UEs beingserved by the RN are performed together.

A specific example of the TAU process in a case where the TAU processesof the UEs being served by the RN are performed together is disclosed.

FIG. 45 is a diagram showing a sequence of a TAU process in a case wherethe TAU processes of the UEs being served by the RN are performedtogether. FIG. 45 shows a case of the TAU between MMEs.

In Steps ST4501 to ST4504, a large number of UEs being served by an RNsimultaneously activate the TAU and transmit a TAU request signal to theRN. The RN that has received a large number of TAU request signalsincludes those in one TAU request message together with the identitiesof the UEs that have transmitted the information included in the TAUrequest signal.

In Step ST4505, the RN transmits this one TAU request message to thetarget MME for UE.

In Step ST4506, the target MME for UE transmits, to the source MME forUE, one signal including pieces of context require information of allthe UEs being served by the RN.

In Step ST4507, the source MME for UE transmits, to the target MME forUE, one signal including contexts of all the UEs being served by the RN.

In Step ST4508, the target MME for UE transmits, to the source MME forUE, one signal including context acceptance successes of all the UEsbeing served by the RN.

In Step ST4509, the target MME for UE transmits, to the HSS, one signalincluding pieces of location update request information of all the UEsbeing served by the RN.

In Step ST4510, the HSS transmits, to the source MME for UE, one signalincluding pieces of location cancellation request information of all theUEs being served by the RN.

The source MME for UE cancels the locations of all the UEs being servedby the RN. In Step ST4511, then, the source MME for UE transmits, to theHSS, a signal indicative of the location cancellation successes of allthe UEs being served by the RN.

The HSS performs the process of updating locations of all the UEs beingserved by the RN. In Step ST4512, then, the HSS transmits, to the targetMME for UE, a location update completion signal indicative of all theUEs being served by the RN.

The target MME for UE performs TAU processes of all the UEs being servedby the RN. In Step ST4513, then, the target MME for UE transmits, to theRN, one signal including pieces of TAU accept information of all the UEsbeing served by the RN.

In Steps ST4514 to ST4517, the RN transmits the TAU acceptance signal tothe UEs being served thereby.

The UEs that have received the TAU acceptance signal perform the TAUprocess, for example, updates the TAI list. In Steps ST4518 to ST4521,then, the UE transmits a TAU completion signal to the RN.

The RN that has received a large number of TAU completion signalsincludes those in one TAU completion message together with theidentities of the UEs that have transmitted the information included inthe TAU completion signal. At this time, the information common to allUEs and information dedicated to a UE may be differentiated such thatthe common information may be included in one signal as UE commoninformation.

In Step ST4522, the RN transmits this one TAU completion message to thetarget MME for UE.

When the signal described above includes pieces of information of allthe UEs being served by the RN, associations may be established togetherwith the UE identities such that every association between informationand UE is evident. They may be included in one message as a list.

The information common to all the UEs and the information dedicated to aUE may be differentiated such that the common information may beincluded in one signal as UE common information. This results in areduction of information amount.

The UE having poor communication quality with an RN may not transmit aTAU request signal to the RN. In such a case, the RN will have keptwaiting the TAU request signal from the UE until the communicationquality with the UE becomes good. If the RN keeps waiting a TAU requestsignal, a large control delay is caused and, at worst, the TAU processesof all the UEs being served by the RN cannot be performed.

In order to solve this problem, a period, which spans from a time atwhich an RN receives a large number of TAU request signals of UEs beingserved thereby to a time at which the RN transmits the one TAU requestmessage to the target MME for RN, may be taken as a predeterminedperiod.

For example, the RN receives a TAU request signal from a UE being servedthereby and, after a lapse of the predetermined period, transmits a TAUrequest message to the target MME for UE. The RN transmits one TAUrequest message, which includes the TAU request signals from all the UEsbeing served by the RN that have been received during the predeterminedperiod, to the target MME for UE.

Through the above, a control delay can be reduced, allowing the RN toperform the TAU processes of UEs being served thereby as many aspossible.

The predetermined period may be managed by a timer. The RN starts thetimer upon receipt of a first TAU request signal from a UE being servedthereby and, when the timer expires, transmits the TAU request signalsfrom the UEs being served thereby that have been received so far, byincluding those in one TAU request message, to the target MME for UE.

The predetermined period may be set by the RN or may be set by the MMEand notified the RN. Alternatively, the predetermined period may benotified the RN from the OAM being a node that holds and manages the RN.

The use of the method disclosed in this embodiment prevents theconcentration of signaling loads on the core network side with respectto the RN also in a case where a large number of UEs being served by anRN simultaneously activate the TAU and the TAU processes of the largenumber of UEs are simultaneously performed, resulting in reductions incontrol delays and TAU process failures.

Tenth Embodiment

This embodiment discloses another method for solving a problem that whenan RN moves, a source MME and a target MME cannot recognize a UE beingserved by the RN and communication between the UE and core network isnot allowed.

The UE being served by the mobile RN regularly or periodically activatesthe TAU. As a result, the TAU process of the UE being served by themobile RN is performed, enabling the MME to perform the mobilitymanagement of the UE. This allows for communication between the UE andcore network.

The MME or mobile RN sets the TAU period of the UE and notifies the UEbeing served by the mobile RN of the TAU period. In a case where the MMEsets the TAU period, the MME may notify the mobile RN using the S1signaling or using the S1 signaling and the signaling on a Un interface,and then, the mobile RN may notify the UE being served thereby. As themethod of notifying from the mobile RN to the UE being served thereby,the TAU period may be included in the system information and then bebroadcast or may be notified in dedicated information. Alternatively,the TAU period may be included in an RN configuration parameter and thennotified.

For an RN that supports the fixed mode and mobile mode, the TAU periodfor fixed mode and the TAU period for mobile mode may be set.

In a case where a UE being served by a mobile RN regularly orperiodically activates the TAU, if the RN moves while the UE isactivating the TAU, an MME cannot recognize the location of the UE, andthus cannot perform the mobility management. As a result, communicationbetween the UE and core network is not allowed while the TAU is beingactivated. In order to shorten the period in which a mobile RN is notallowed communication, the TAU period of the mobile mode may beshortened. More specifically, the TAU period in the mobile mode may beshortened compared with the TAU period of the RN in the fixed mode orother cell (eNB). Consequently, the period in which the MME cannotperform the UE mobility management can be shortened.

In a case where the MME or RN makes a notification through dedicatedsignaling, the TAU period may differ from one UE to another.Alternatively, the TAU period may be set randomly from one UE toanother.

The MME or RN may set the allowable TAU period range and notify a UEbeing served thereby. The UE is configured to individually select theTAU period from the allowable TAU period range at random.

As a result, the TAU process from the UE being served by the RN israndomly activated, preventing a control delay and a TAU process failurecaused by the concentration of TAU processes among the UE, RN, and corenetwork.

The method disclosed in this embodiment causes the TAU process of a UEbeing served by the mobile RN to be performed, allowing the MME toperform the mobility management of the UE. This allows for communicationbetween the UE and core network.

In the methods disclosed in the present invention, the MME for RN andthe MME for UE may be configured in the same MME. In a case where theMME for RN and the MME for UE are configured in the same MME, signalingbetween the MME for RN and the MME for UE is performed in the same MME,which does not require signaling between the MME for RN and the MME forUE.

The methods disclosed in the present invention are applicable not onlyto the case in which the RN performs the HO process but also to the casein which the RN selects or reselects a cell. Specifically, the method isalso applicable to a case in which the RN reselects a cell as a resultof moving, a case in which the power of the RN is turned off and thenturned on again, or a case in which the communication quality between anRN and a DeNB declines and an RN thus selects or reselects a cell aftera radio link failure. Also in this case, the TAU processes of the RN andthe UE being served thereby are allowed such that communication betweenthe UE being served by the RN and the core network is allowed.

The methods disclosed in the present invention can be appropriatelycarried out in combination. The control according to a situation of asystem such as UE, relay, eNB, or MME can be performed.

It has been described that, as the method of dividing relay resources, alink from a DeNB to an RN and a link from an RN to a UE aretime-division multiplexed in one frequency band and a link from the RNto the DeNB and a link from the UE to the RN are also time-divisionmultiplexed in one frequency band. However, not limited to the above,and other division method may be used.

For example, the link from the DeNB to the RN and the link from the RNto the UE may be frequency-division multiplexed in different carriers orfrequency bands, and the link from the RN to the DeNB and the link fromthe UE to the RN may also be frequency-division multiplexed in differentcarriers or frequency bands. The methods disclosed in the first to tenthembodiments described above are applicable.

The methods disclosed in the present invention are applicable not onlyto a relay node but also to an RRU, RRE, RRH, and the like to beconnected to an eNB. For example, the RRH and eNB are wirelesslyconnected. It suffices that the access link between the RN and UE isapplied to the radio link between the RRH and UE and the backhaul linkbetween the DeNB and RN is applied to the radio link between the eNB andRRH. This allows for communication between a UE being served by an RRHand a core network also in a case where the RRH moves. The same holdstrue for an RRU and an RRE. The RRU, RRE, and RRH correspond to a relaydevice.

The methods disclosed in the present invention are applicable not onlyto a relay node but also to a HeNB. The HeNB and MME or the HeNB andHeNBGW are wirelessly connected. The access link between the RN and UEmay be applied to the radio link between the HeNB and UE, and the linkbetween the MME and RN that includes the backhaul link between the DeNBand RN may be applied to the radio link between the MME and HeNB.Alternatively, the link between the MME and RN that includes thebackhaul link between the DeNB and RN may be applied to the radio linkbetween the HeNBGW and HeNB. This allows for communication between theUE being served by a HeNB and a core network in a case where the HeNBmoves. The HeNB corresponds to a relay device.

The methods disclosed in the present invention are applicable not onlyto a relay node but also to any node or device that has functions andmodes of both of the user equipment and base station. The node or devicethat has functions and modes of both of the user equipment and basestation corresponds to a relay device.

As described above, the methods disclosed in the present invention areapplicable, as a DeNB that serves a relay, not only to normal eNBs(macro cells) but also to so-called local nodes such as pico eNB (picocell), HeNB (femtocell), node for hotzone cell, relay node, and remoteradio head (RRH). The local node corresponds to a relay device.

The embodiments above have described a user equipment (UE) carried by apassenger in a moving body such as an express bus or high-speed rail,not limited thereto. The embodiments above are also applicable tocommunication equipments not required to be operated by a person. Theembodiments above are also applicable to an equipment (MTC device) formachine type communication (MTC) as the communication equipment notrequired to be operated by a person. The communication equipmentcorresponds to a user equipment device.

While the embodiments above have described the RN in the LTE-A, thecommunication system of the present invention is also applicable to acase in which relay communication is performed in other communicationsystem or a case in which relay communication is performed in aheterogenous communication system.

While the invention has been shown and described in detail, theforegoing description is in all aspects illustrative and notrestrictive. It is therefore understood that numerous modifications andvariations can be devised without departing from the scope of theinvention.

DESCRIPTION OF REFERENCE SYMBOLS

1501 second MME, 1502 to 1507 seventh to twelfth eNBs (cells), 1508relay node (RN), 1509 user equipment (UE), 1511 to 1516 seventh totwelfth coverages, 1602 third TA, 1519 fourth TA, 1520 first MME, 1522to 1527 first to sixth eNBs (cells), 1528 to 1533 first to sixthcoverages, 1601 first TA, 1535 second TA.

The invention claimed is:
 1. A mobile communication system comprising: aplurality of base station devices to be connected to a core network; auser equipment device configured to perform radio communications withsaid plurality of base station devices; and a mobile relay devicemovably configured to relay said radio communications between saidplurality of base station devices and said user equipment device,wherein said core network includes a mobility management entity thatmanages said plurality of base station devices, said user equipmentdevice, and said mobile relay device per predetermined tracking area, amobile relay device tracking area of said mobile relay device is notchanged as a result of moving of said mobile relay device, said mobilitymanagement entity includes: a first mobility management entity thatmanages a mobility of said user equipment device being served by saidplurality of base station devices per said predetermined tracking area;and a second mobility management entity that manages only said mobilerelay device tracking area among a plurality of tracking areas andmanages a mobility of said user equipment device being served by saidmobile relay device without managing the mobility of any user equipmentbeing served by any of said plurality of base station devices.
 2. Themobile communication system according to claim 1, wherein said secondmobility management entity is provided separately from said firstmobility management entity.
 3. The mobile communication system accordingto claim 1, wherein said second mobility management entity is providedtogether with said first mobility management entity.
 4. The mobilecommunication system according to claim 1, wherein said second mobilitymanagement entity is provided together with a specific mobilitymanagement entity to which a specific base station device belongs, amonga plurality of said first mobility management entities, said specificbase station device being a base station device connectable with saidmobile relay device.